ts-11-mini-sql

# In-memory SQL SELECT engine

Implement a file **`solution.ts`** that parses a small `SELECT` statement and executes
it against an in-memory table of rows. This is a parser + interpreter exercise: you must
tokenize the query, build a small AST, validate it, and evaluate it over the data.

## Types to export

```ts
export type Row = Record<string, number | string>;

export class QueryError extends Error {}

// Parse and execute a small SQL SELECT against the given rows. Returns the result rows.
export function query(sql: string, rows: Row[]): Row[];
```

The `rows` argument **is** the table; the table name in the query is accepted but
otherwise ignored (the data comes from `rows` regardless of the name written).

## Grammar

```
SELECT <cols> FROM <table> [WHERE <cond>] [ORDER BY <col> [ASC|DESC]] [LIMIT <n>]
```

The clauses, when present, must appear in exactly this order. The four optional clauses
(`WHERE`, `ORDER BY`, `LIMIT`) are each optional and independent.

### `<cols>`

- `*` selects **all** columns. Each result row preserves that source row's own key
  insertion order (rows are copied; no column is renamed or reordered).
- Otherwise a comma-separated list of column names, e.g. `name, age`. The result rows
  then contain **exactly** those columns, **in the listed order**. A selected column that
  is missing from a given source row is simply omitted from that row's output (it is not
  an error, and no placeholder value is inserted).

### `<table>`

A bare identifier (letters, digits, `_`, not starting with a digit). Any name is accepted.

### `<cond>` (the `WHERE` clause)

One or more comparisons combined with `AND` / `OR`. There are **no parentheses**.
`AND` binds **tighter** than `OR`, so

```
a = 1 AND b = 2 OR c = 3
```

parses as `(a = 1 AND b = 2) OR (c = 3)`.

A single comparison is `col <op> value` where:

- `<op>` is one of `=  !=  <  >  <=  >=`.
- `value` is either an **integer literal** (optionally signed, e.g. `42`, `-3`, `0`) or a
  **single-quoted string** (e.g. `'alice'`). Strings may contain spaces; an unterminated
  string literal is an error.

Comparison semantics, given `cell = row[col]`:

- `=` / `!=` work for both numbers and strings using strict (in)equality. If `cell` is a
  number and `value` is a string (or vice versa), they are considered **not equal** (so
  `=` is `false`, `!=` is `true`).
- `<  >  <=  >=` are ordering comparisons:
  - both number  -> numeric comparison;
  - both string  -> lexicographic comparison (JavaScript `<`/`>` on strings);
  - **type mismatch** (one number, one string) -> the comparison is **`false`**.
- If `col` is **not present** in the row, the comparison is treated as a non-match:
  `=` is `false`, `!=` is `true`, and every ordering comparison is `false`. This does
  **not** throw — only *syntactically* invalid queries throw.

A row is included iff the whole `<cond>` evaluates to true for it. With no `WHERE`, all
rows match.

### `ORDER BY <col> [ASC|DESC]`

Sort the result by a single column. `ASC` (the default) sorts ascending; `DESC`
descending. Numbers sort numerically, strings lexicographically. The sort must be
**stable**: rows that compare equal keep their relative input order. A mismatched-type or
missing sort key compares as equal to the others (it does not throw and does not crash);
ties are broken by stability (original order).

### `LIMIT <n>`

Keep the first `n` result rows after ordering. `n` must be a **non-negative integer**.

### Case sensitivity

Keywords (`SELECT`, `FROM`, `WHERE`, `AND`, `OR`, `ORDER`, `BY`, `ASC`, `DESC`, `LIMIT`)
are **case-insensitive** — `select` and `SELECT` are equivalent. Column names and quoted
string values are **case-sensitive**.

## Evaluation order

`WHERE` filtering -> `ORDER BY` sorting -> `LIMIT` truncation -> column projection.
(Projection last means you may order by a column you did not select.)

## Errors — throw `QueryError`

Throw a `QueryError` (not a plain `Error`) for any **syntactically invalid** query,
including:

- a statement that does not start with `SELECT`, or has no `FROM`;
- an empty column list, or a trailing/embedded comma in the column list;
- an unknown clause / leftover tokens after a valid statement;
- a bad comparison operator, or a comparison missing its column / operator / value;
- an unterminated single-quoted string;
- a `LIMIT` whose argument is missing or is not a non-negative integer;
- an `ORDER BY` without a column.

Referencing a column that is absent from a particular row at **evaluation** time (in
`WHERE` or `ORDER BY`) is **not** an error — see the semantics above.

## Worked example

```ts
const rows: Row[] = [
  { id: 1, name: "alice", age: 30 },
  { id: 2, name: "bob", age: 25 },
  { id: 3, name: "carol", age: 30 },
  { id: 4, name: "dave", age: 17 },
];

query(
  "SELECT name, age FROM users WHERE age >= 18 ORDER BY age DESC LIMIT 2",
  rows,
);
// WHERE drops dave (17). Remaining: alice(30), bob(25), carol(30).
// ORDER BY age DESC (stable): alice(30), carol(30), bob(25).
// LIMIT 2:                    alice(30), carol(30).
// Projection name, age:
// -> [ { name: "alice", age: 30 }, { name: "carol", age: 30 } ]
```

Keep it fully typed: `solution.ts` must pass `tsc --noEmit` in strict mode. Do not use
`any` in the implementation; prefer `unknown` and narrow.

import { test } from "node:test";
import { strict as assert } from "node:assert";
import { query, QueryError, type Row } from "./solution.ts";

function people(): Row[] {
  return [
    { id: 1, name: "alice", age: 30, city: "NYC" },
    { id: 2, name: "bob", age: 25, city: "LA" },
    { id: 3, name: "carol", age: 30, city: "NYC" },
    { id: 4, name: "dave", age: 17, city: "SF" },
  ];
}

test("SELECT * preserves all columns and per-row key order", () => {
  const rows: Row[] = [{ z: 1, a: "x", m: 2 }];
  const out = query("SELECT * FROM t", rows);
  assert.deepEqual(out, [{ z: 1, a: "x", m: 2 }]);
  assert.deepEqual(Object.keys(out[0]!), ["z", "a", "m"]);
  // Result is a copy, not the same object.
  assert.notEqual(out[0], rows[0]);
});

test("explicit column list selects exactly those columns in order", () => {
  const out = query("SELECT name, id FROM users", people());
  assert.deepEqual(out, [
    { name: "alice", id: 1 },
    { name: "bob", id: 2 },
    { name: "carol", id: 3 },
    { name: "dave", id: 4 },
  ]);
  assert.deepEqual(Object.keys(out[0]!), ["name", "id"]);
});

test("selected column missing from a row is omitted, not an error", () => {
  const rows: Row[] = [{ a: 1, b: 2 }, { a: 3 }];
  const out = query("SELECT a, b FROM t", rows);
  assert.deepEqual(out, [{ a: 1, b: 2 }, { a: 3 }]);
});

test("WHERE = and != on numbers", () => {
  assert.deepEqual(
    query("SELECT name FROM u WHERE age = 30", people()),
    [{ name: "alice" }, { name: "carol" }],
  );
  assert.deepEqual(
    query("SELECT name FROM u WHERE age != 30", people()),
    [{ name: "bob" }, { name: "dave" }],
  );
});

test("WHERE = and != on strings (case-sensitive values)", () => {
  assert.deepEqual(
    query("SELECT name FROM u WHERE city = 'NYC'", people()),
    [{ name: "alice" }, { name: "carol" }],
  );
  // Wrong case does not match.
  assert.deepEqual(query("SELECT name FROM u WHERE city = 'nyc'", people()), []);
  assert.deepEqual(
    query("SELECT name FROM u WHERE name != 'alice'", people()).length,
    3,
  );
});

test("numeric ordering comparisons < > <= >=", () => {
  assert.deepEqual(
    query("SELECT name FROM u WHERE age < 30", people()),
    [{ name: "bob" }, { name: "dave" }],
  );
  assert.deepEqual(
    query("SELECT name FROM u WHERE age > 25", people()),
    [{ name: "alice" }, { name: "carol" }],
  );
  assert.deepEqual(
    query("SELECT name FROM u WHERE age <= 25", people()),
    [{ name: "bob" }, { name: "dave" }],
  );
  assert.deepEqual(
    query("SELECT name FROM u WHERE age >= 30", people()),
    [{ name: "alice" }, { name: "carol" }],
  );
});

test("lexicographic string ordering comparisons", () => {
  assert.deepEqual(
    query("SELECT name FROM u WHERE name < 'carol'", people()),
    [{ name: "alice" }, { name: "bob" }],
  );
  assert.deepEqual(
    query("SELECT name FROM u WHERE name >= 'carol'", people()),
    [{ name: "carol" }, { name: "dave" }],
  );
});

test("negative integer literals", () => {
  const rows: Row[] = [{ t: -5 }, { t: 0 }, { t: 3 }];
  assert.deepEqual(query("SELECT t FROM r WHERE t < 0", rows), [{ t: -5 }]);
  assert.deepEqual(query("SELECT t FROM r WHERE t = -5", rows), [{ t: -5 }]);
  assert.deepEqual(query("SELECT t FROM r WHERE t >= -5", rows), [
    { t: -5 },
    { t: 0 },
    { t: 3 },
  ]);
});

test("AND binds tighter than OR", () => {
  const rows: Row[] = [
    { a: 1, b: 2, c: 9 }, // a=1 AND b=2 -> true
    { a: 1, b: 5, c: 3 }, // c=3 -> true via OR
    { a: 9, b: 9, c: 9 }, // none -> false
  ];
  // (a = 1 AND b = 2) OR (c = 3)
  const out = query("SELECT a FROM t WHERE a = 1 AND b = 2 OR c = 3", rows);
  assert.deepEqual(out, [{ a: 1 }, { a: 1 }]);
});

test("OR then AND precedence: a = 1 OR a = 2 AND b = 9", () => {
  const rows: Row[] = [
    { a: 1, b: 0 }, // a=1 -> true
    { a: 2, b: 9 }, // a=2 AND b=9 -> true
    { a: 2, b: 0 }, // a=2 but b!=9 -> false
  ];
  // parses as a = 1 OR (a = 2 AND b = 9)
  const out = query("SELECT a, b FROM t WHERE a = 1 OR a = 2 AND b = 9", rows);
  assert.deepEqual(out, [{ a: 1, b: 0 }, { a: 2, b: 9 }]);
});

test("ORDER BY ascending (default) and DESC", () => {
  const asc = query("SELECT name FROM u ORDER BY age", people());
  assert.deepEqual(asc.map((r) => r["name"]), ["dave", "bob", "alice", "carol"]);
  const desc = query("SELECT name FROM u ORDER BY age DESC", people());
  assert.deepEqual(desc.map((r) => r["name"]), ["alice", "carol", "bob", "dave"]);
});

test("ORDER BY is stable for equal keys", () => {
  // alice and carol both have age 30; original order alice before carol.
  const asc = query("SELECT name FROM u ORDER BY age ASC", people());
  const names = asc.map((r) => r["name"]);
  assert.ok(names.indexOf("alice") < names.indexOf("carol"));
  const desc = query("SELECT name FROM u ORDER BY age DESC", people());
  const dnames = desc.map((r) => r["name"]);
  // Stability preserved under DESC too: equal keys keep input order.
  assert.ok(dnames.indexOf("alice") < dnames.indexOf("carol"));
});

test("ORDER BY a column not in the SELECT list, plus LIMIT", () => {
  const out = query(
    "SELECT name FROM u WHERE age >= 18 ORDER BY age DESC LIMIT 2",
    people(),
  );
  assert.deepEqual(out, [{ name: "alice" }, { name: "carol" }]);
});

test("LIMIT keeps first n and LIMIT 0 yields empty", () => {
  assert.deepEqual(
    query("SELECT id FROM u ORDER BY id LIMIT 2", people()),
    [{ id: 1 }, { id: 2 }],
  );
  assert.deepEqual(query("SELECT id FROM u LIMIT 0", people()), []);
  // LIMIT larger than result is fine.
  assert.deepEqual(query("SELECT id FROM u ORDER BY id LIMIT 99", people()).length, 4);
});

test("type-mismatch comparisons: = is false, != is true, ordering is false", () => {
  const rows: Row[] = [{ v: 5 }, { v: "5" }];
  // number cell vs string literal
  assert.deepEqual(query("SELECT v FROM t WHERE v = '5'", rows), [{ v: "5" }]);
  assert.deepEqual(query("SELECT v FROM t WHERE v != '5'", rows), [{ v: 5 }]);
  // ordering of number cell vs string literal is a type mismatch -> false,
  // but the string cell "5" vs string literal '9' is a valid string comparison.
  assert.deepEqual(query("SELECT v FROM t WHERE v < '9'", rows), [{ v: "5" }]);
  // numeric cell 5 vs string '9' is a mismatch (false); string cell "5" vs number 0 too.
  assert.deepEqual(query("SELECT v FROM t WHERE v > 0", rows), [{ v: 5 }]);
});

test("missing column in WHERE: = false, != true, ordering false (no throw)", () => {
  const rows: Row[] = [{ a: 1 }, { a: 2 }];
  assert.deepEqual(query("SELECT a FROM t WHERE missing = 1", rows), []);
  assert.deepEqual(query("SELECT a FROM t WHERE missing != 1", rows), [{ a: 1 }, { a: 2 }]);
  assert.deepEqual(query("SELECT a FROM t WHERE missing > 0", rows), []);
});

test("ORDER BY with missing / mismatched keys does not throw", () => {
  const rows: Row[] = [{ a: 2 }, { b: 1 }, { a: 1 }];
  // Rows without `a` compare as equal; should not throw.
  const out = query("SELECT * FROM t ORDER BY a", rows);
  assert.equal(out.length, 3);
});

test("keywords are case-insensitive; identifiers/strings are not", () => {
  const out = query(
    "select Name from u WHERE City = 'NYC' order by Age desc limit 1",
    people().map((r) => ({ Name: String(r["name"]), City: String(r["city"]), Age: Number(r["age"]) })),
  );
  assert.deepEqual(out, [{ Name: "alice" }]);
  // Mixed-case keywords work too.
  assert.deepEqual(
    query("SeLeCt id FrOm u Where age = 25", people()),
    [{ id: 2 }],
  );
});

test("no WHERE returns all rows; whitespace is tolerated", () => {
  assert.equal(query("  SELECT   *   FROM   t  ", people()).length, 4);
});

test("throws: missing SELECT", () => {
  assert.throws(() => query("FROM t", []), QueryError);
});

test("throws: missing FROM", () => {
  assert.throws(() => query("SELECT *", []), QueryError);
  assert.throws(() => query("SELECT a, b", []), QueryError);
});

test("throws: empty / malformed column list", () => {
  assert.throws(() => query("SELECT FROM t", []), QueryError);
  assert.throws(() => query("SELECT a, FROM t", []), QueryError);
  assert.throws(() => query("SELECT , a FROM t", []), QueryError);
});

test("throws: bad operator and malformed comparison", () => {
  assert.throws(() => query("SELECT * FROM t WHERE a == 1", []), QueryError);
  assert.throws(() => query("SELECT * FROM t WHERE a 1", []), QueryError);
  assert.throws(() => query("SELECT * FROM t WHERE a =", []), QueryError);
  assert.throws(() => query("SELECT * FROM t WHERE = 1", []), QueryError);
});

test("throws: unterminated string literal", () => {
  assert.throws(() => query("SELECT * FROM t WHERE name = 'alice", []), QueryError);
});

test("throws: bad LIMIT (missing, negative, non-integer, string)", () => {
  assert.throws(() => query("SELECT * FROM t LIMIT", []), QueryError);
  assert.throws(() => query("SELECT * FROM t LIMIT -1", []), QueryError);
  assert.throws(() => query("SELECT * FROM t LIMIT 'x'", []), QueryError);
});

test("throws: unknown clause / leftover tokens", () => {
  assert.throws(() => query("SELECT * FROM t GROUP BY a", []), QueryError);
  assert.throws(() => query("SELECT * FROM t WHERE a = 1 b = 2", []), QueryError);
  assert.throws(() => query("SELECT * FROM t ORDER BY", []), QueryError);
});

You are an expert programmer. Solve the task exactly as specified. Output your solution as fenced code blocks using the required file name(s) and the exact function/type signatures requested. Prefer correctness; do not include prose outside code unless asked.

```ts
export type Row = Record<string, number | string>;

export class QueryError extends Error {}

type Token = {
  type: 'keyword' | 'identifier' | 'operator' | 'value' | 'comma' | 'eof';
  value: string;
  line: number;
  column: number;
};

type ASTNode =
  | { type: 'select'; columns: string[]; table: string; where?: WhereClause; orderBy?: OrderByClause; limit?: number }
  | { type: 'where'; condition: Condition }
  | { type: 'condition'; left: string; operator: string; right: string | number }
  | { type: 'orderBy'; column: string; direction: 'asc' | 'desc' }
  | { type: 'limit'; count: number };

type WhereClause = {
  type: 'where';
  condition: Condition;
};

type OrderByClause = {
  type: 'orderBy';
  column: string;
  direction: 'asc' | 'desc';
};

type Condition = 
  | { type: 'comparison'; left: string; operator: string; right: string | number }
  | { type: 'logical'; left: Condition; operator: 'AND' | 'OR'; right: Condition };

const KEYWORDS = new Set(['SELECT', 'FROM', 'WHERE', 'ORDER', 'BY', 'ASC', 'DESC', 'LIMIT']);
const OPERATORS = new Set(['=', '!=', '<', '>', '<=', '>=']);

function tokenize(sql: string): Token[] {
  const tokens: Token[] = [];
  let i = 0;
  let line = 1;
  let column = 0;

  while (i < sql.length) {
    const char = sql[i];
    
    if (char === ' ' || char === '\t') {
      i++;
      column++;
      continue;
    }
    
    if (char === '\n') {
      line++;
      column = 0;
      i++;
      continue;
    }
    
    if (char === "'") {
      // String literal
      let j = i + 1;
      let value = "'";
      while (j < sql.length && sql[j] !== "'") {
        value += sql[j];
        j++;
      }
      if (j >= sql.length) {
        throw new QueryError(`Unterminated string literal`);
      }
      value += "'";
      tokens.push({ type: 'value', value, line, column });
      i = j + 1;
      column = j + 1;
      continue;
    }
    
    if (char === ',') {
      tokens.push({ type: 'comma', value: ',', line, column });
      i++;
      column++;
      continue;
    }
    
    if (/[a-zA-Z_]/.test(char)) {
      // Identifier or keyword
      let j = i;
      while (j < sql.length && /[a-zA-Z0-9_]/.test(sql[j])) {
        j++;
      }
      const value = sql.substring(i, j).toUpperCase();
      tokens.push({ type: 'keyword', value, line, column });
      i = j;
      column = j;
      continue;
    }
    
    if (/[0-9]/.test(char)) {
      // Number literal
      let j = i;
      while (j < sql.length && /[0-9]/.test(sql[j])) {
        j++;
      }
      const value = sql.substring(i, j);
      tokens.push({ type: 'value', value, line, column });
      i = j;
      column = j;
      continue;
    }
    
    if (['=', '<', '>'].includes(char)) {
      // Operators
      let j = i;
      while (j < sql.length && ['=', '<', '>'].includes(sql[j])) {
        j++;
      }
      const value = sql.substring(i, j);
      tokens.push({ type: 'operator', value, line, column });
      i = j;
      column = j;
      continue;
    }
    
    // Unknown character
    throw new QueryError(`Unexpected character: ${char}`);
  }
  
  tokens.push({ type: 'eof', value: '', line, column });
  return tokens;
}

function parse(tokens: Token[]): ASTNode {
  let pos = 0;
  
  function consume(expectedType: string, expectedValue?: string): Token {
    if (pos >= tokens.length) {
      throw new QueryError(`Unexpected end of query`);
    }
    
    const token = tokens[pos];
    if (token.type !== expectedType || (expectedValue && token.value !== expectedValue)) {
      throw new QueryError(`Expected ${expectedType} ${expectedValue ? `'${expectedValue}'` : ''}, got ${token.type} '${token.value}'`);
    }
    
    pos++;
    return token;
  }
  
  function peek(): Token {
    if (pos >= tokens.length) {
      return { type: 'eof', value: '', line: 0, column: 0 };
    }
    return tokens[pos];
  }
  
  // SELECT
  const selectToken = consume('keyword', 'SELECT');
  
  // Columns
  const columns: string[] = [];
  while (peek().type !== 'keyword' || peek().value !== 'FROM') {
    if (peek().type === 'eof') {
      throw new QueryError(`Expected FROM clause`);
    }
    
    if (peek().type === 'identifier') {
      columns.push(peek().value);
      pos++;
    } else if (peek().type === 'comma') {
      if (columns.length === 0) {
        throw new QueryError(`Empty column list`);
      }
      pos++; // consume comma
    } else {
      throw new QueryError(`Expected identifier or comma, got ${peek().type}`);
    }
    
    // Check for trailing comma
    if (peek().type === 'keyword' && peek().value === 'FROM') {
      break;
    }
  }
  
  if (columns.length === 0) {
    throw new QueryError(`Empty column list`);
  }
  
  // FROM
  consume('keyword', 'FROM');
  const tableToken = consume('identifier');
  const table = tableToken.value;
  
  let whereClause: WhereClause | undefined;
  let orderByClause: OrderByClause | undefined;
  let limitValue: number | undefined;
  
  // WHERE
  if (peek().type === 'keyword' && peek().value === 'WHERE') {
    pos++; // consume WHERE
    const condition = parseCondition();
    whereClause = { type: 'where', condition };
  }
  
  // ORDER BY
  if (peek().type === 'keyword' && peek().value === 'ORDER') {
    pos++; // consume ORDER
    consume('keyword', 'BY');
    const columnToken = consume('identifier');
    const column = columnToken.value;
    
    let direction: 'asc' | 'desc' = 'asc';
    if (peek().type === 'keyword') {
      if (peek().value === 'ASC') {
        pos++;
      } else if (peek().value === 'DESC') {
        pos++;
        direction = 'desc';
      }
    }
    
    orderByClause = { type: 'orderBy', column, direction };
  }
  
  // LIMIT
  if (peek().type === 'keyword' && peek().value === 'LIMIT') {
    pos++; // consume LIMIT
    const limitToken = consume('value');
    const num = parseInt(limitToken.value);
    if (isNaN(num) || num < 0) {
      throw new QueryError(`Invalid LIMIT value: ${limitToken.value}`);
    }
    limitValue = num;
  }
  
  // Check for unexpected tokens
  if (peek().type !== 'eof') {
    throw new QueryError(`Unexpected token after query: ${peek().value}`);
  }
  
  return {
    type: 'select',
    columns,
    table,
    where: whereClause,
    orderBy: orderByClause,
    limit: limitValue
  };
}

function parseCondition(): Condition {
  return parseLogicalOr();
}

function parseLogicalOr(): Condition {
  let left = parseLogicalAnd();
  
  while (peek().type === 'keyword' && peek().value === 'OR') {
    const operatorToken = consume('keyword', 'OR');
    const right = parseLogicalAnd();
    left = { type: 'logical', left, operator: 'OR', right };
  }
  
  return left;
}

function parseLogicalAnd(): Condition {
  let left = parseComparison();
  
  while (peek().type === 'keyword' && peek().value === 'AND') {
    const operatorToken = consume('keyword', 'AND');
    const right = parseComparison();
    left = { type: 'logical', left, operator: 'AND', right };
  }
  
  return left;
}

function parseComparison(): Condition {
  const leftToken = consume('identifier');
  const left = leftToken.value;
  
  const opToken = consume('operator');
  const op = opToken.value;
  
  if (!OPERATORS.has(op)) {
    throw new QueryError(`Invalid operator: ${op}`);
  }
  
  let rightValue: string | number;
  const valueToken = peek();
  if (valueToken.type === 'value') {
    pos++;
    if (valueToken.value.startsWith("'")) {
      // String literal
      rightValue = valueToken.value.slice(1, -1); // Remove quotes
    } else {
      // Number literal
      const num = parseInt(valueToken.value);
      if (isNaN(num)) {
        throw new QueryError(`Invalid number: ${valueToken.value}`);
      }
      rightValue = num;
    }
  } else {
    throw new QueryError(`Expected value, got ${valueToken.type}`);
  }
  
  return { type: 'comparison', left, operator: op, right: rightValue };
}

function evaluateCondition(row: Row, condition: Condition): boolean {
  if (condition.type === 'comparison') {
    const col = condition.left;
    const op = condition.operator;
    const value = condition.right;
    
    // If column doesn't exist in row, treat as non-match
    if (!(col in row)) {
      return op === '!=' ? true : false;
    }
    
    const cellValue = row[col];
    
    // Type mismatch handling
    if (typeof cellValue === 'number' && typeof value === 'string') {
      return op === '!=' ? true : false;
    }
    if (typeof cellValue === 'string' && typeof value === 'number') {
      return op === '!=' ? true : false;
    }
    
    switch (op) {
      case '=': return cellValue === value;
      case '!=': return cellValue !== value;
      case '<': return cellValue < value;
      case '>': return cellValue > value;
      case '<=': return cellValue <= value;
      case '>=': return cellValue >= value;
      default: return false;
    }
  } else if (condition.type === 'logical') {
    const leftResult = evaluateCondition(row, condition.left);
    const rightResult = evaluateCondition(row, condition.right);
    
    switch (condition.operator) {
      case 'AND': return leftResult && rightResult;
      case 'OR': return leftResult || rightResult;
      default: return false;
    }
  }
  
  return false;
}

function sortRows(rows: Row[], orderBy: OrderByClause): Row[] {
  const sorted = [...rows];
  
  return sorted.sort((a, b) => {
    const col = orderBy.column;
    
    // If column doesn't exist in row, treat as equal
    if (!(col in a) || !(col in b)) {
      return 0;
    }
    
    const aValue = a[col];
    const bValue = b[col];
    
    // Type mismatch handling
    if (typeof aValue === 'number' && typeof bValue === 'string') {
      return 0;
    }
    if (typeof aValue === 'string' && typeof bValue === 'number') {
      return 0;
    }
    
    let result: number;
    if (typeof aValue === 'number' && typeof bValue === 'number') {
      result = aValue - bValue;
    } else {
      // Both are strings
      result = (aValue as string).localeCompare(bValue as string);
    }
    
    return orderBy.direction === 'asc' ? result : -result;
  });
}

function projectRows(rows: Row[], columns: string[]): Row[] {
  return rows.map(row => {
    const newRow: Row = {};
    for (const col of columns) {
      if (col in row) {
        newRow[col] = row[col];
      }
    }
    return newRow;
  });
}

export function query(sql: string, rows: Row[]): Row[] {
  try {
    const tokens = tokenize(sql);
    const ast = parse(tokens);
    
    // WHERE filtering
    let filteredRows = rows;
    if (ast.where) {
      filteredRows = rows.filter(row => evaluateCondition(row, ast.where!.condition));
    }
    
    // ORDER BY sorting
    let sortedRows = filteredRows;
    if (ast.orderBy) {
      sortedRows = sortRows(filteredRows, ast.orderBy);
    }
    
    // LIMIT truncation
    let limitedRows = sortedRows;
    if (ast.limit !== undefined) {
      limitedRows = sortedRows.slice(0, ast.limit);
    }
    
    // Column projection
    let resultRows = limitedRows;
    if (ast.columns[0] === '*') {
      // Select all columns preserving original row structure
      resultRows = limitedRows.map(row => ({ ...row }));
    } else {
      resultRows = projectRows(limitedRows, ast.columns);
    }
    
    return resultRows;
  } catch (error) {
    if (error instanceof QueryError) {
      throw error;
    }
    throw new QueryError(`Invalid query: ${error}`);
  }
}
```

[
  {
    "total": 26,
    "answer": "```ts\nexport type Row = Record<string, number | string>;\n\nexport class QueryError extends Error {}\n\ntype Token = {\n  type: 'keyword' | 'identifier' | 'operator' | 'value' | 'comma' | 'eof';\n  value: string;\n  line: number;\n  column: number;\n};\n\ntype ASTNode =\n  | { type: 'select'; columns: string[]; table: string; where?: WhereClause; orderBy?: OrderByClause; limit?: number }\n  | { type: 'where'; condition: Condition }\n  | { type: 'condition'; left: string; operator: string; right: string | number }\n  | { type: 'orderBy'; column: string; direction: 'asc' | 'desc' }\n  | { type: 'limit'; count: number };\n\ntype WhereClause = {\n  type: 'where';\n  condition: Condition;\n};\n\ntype OrderByClause = {\n  type: 'orderBy';\n  column: string;\n  direction: 'asc' | 'desc';\n};\n\ntype Condition = \n  | { type: 'comparison'; left: string; operator: string; right: string | number }\n  | { type: 'logical'; left: Condition; operator: 'AND' | 'OR'; right: Condition };\n\nconst KEYWORDS = new Set(['SELECT', 'FROM', 'WHERE', 'ORDER', 'BY', 'ASC', 'DESC', 'LIMIT']);\nconst OPERATORS = new Set(['=', '!=', '<', '>', '<=', '>=']);\n\nfunction tokenize(sql: string): Token[] {\n  const tokens: Token[] = [];\n  let i = 0;\n  let line = 1;\n  let column = 0;\n\n  while (i < sql.length) {\n    const char = sql[i];\n    \n    if (char === ' ' || char === '\\t') {\n      i++;\n      column++;\n      continue;\n    }\n    \n    if (char === '\\n') {\n      line++;\n      column = 0;\n      i++;\n      continue;\n    }\n    \n    if (char === \"'\") {\n      // String literal\n      let j = i + 1;\n      let value = \"'\";\n      while (j < sql.length && sql[j] !== \"'\") {\n        value += sql[j];\n        j++;\n      }\n      if (j >= sql.length) {\n        throw new QueryError(`Unterminated string literal`);\n      }\n      value += \"'\";\n      tokens.push({ type: 'value', value, line, column });\n      i = j + 1;\n      column = j + 1;\n      continue;\n    }\n    \n    if (char === ',') {\n      tokens.push({ type: 'comma', value: ',', line, column });\n      i++;\n      column++;\n      continue;\n    }\n    \n    if (/[a-zA-Z_]/.test(char)) {\n      // Identifier or keyword\n      let j = i;\n      while (j < sql.length && /[a-zA-Z0-9_]/.test(sql[j])) {\n        j++;\n      }\n      const value = sql.substring(i, j).toUpperCase();\n      tokens.push({ type: 'keyword', value, line, column });\n      i = j;\n      column = j;\n      continue;\n    }\n    \n    if (/[0-9]/.test(char)) {\n      // Number literal\n      let j = i;\n      while (j < sql.length && /[0-9]/.test(sql[j])) {\n        j++;\n      }\n      const value = sql.substring(i, j);\n      tokens.push({ type: 'value', value, line, column });\n      i = j;\n      column = j;\n      continue;\n    }\n    \n    if (['=', '<', '>'].includes(char)) {\n      // Operators\n      let j = i;\n      while (j < sql.length && ['=', '<', '>'].includes(sql[j])) {\n        j++;\n      }\n      const value = sql.substring(i, j);\n      tokens.push({ type: 'operator', value, line, column });\n      i = j;\n      column = j;\n      continue;\n    }\n    \n    // Unknown character\n    throw new QueryError(`Unexpected character: ${char}`);\n  }\n  \n  tokens.push({ type: 'eof', value: '', line, column });\n  return tokens;\n}\n\nfunction parse(tokens: Token[]): ASTNode {\n  let pos = 0;\n  \n  function consume(expectedType: string, expectedValue?: string): Token {\n    if (pos >= tokens.length) {\n      throw new QueryError(`Unexpected end of query`);\n    }\n    \n    const token = tokens[pos];\n    if (token.type !== expectedType || (expectedValue && token.value !== expectedValue)) {\n      throw new QueryError(`Expected ${expectedType} ${expectedValue ? `'${expectedValue}'` : ''}, got ${token.type} '${token.value}'`);\n    }\n    \n    pos++;\n    return token;\n  }\n  \n  function peek(): Token {\n    if (pos >= tokens.length) {\n      return { type: 'eof', value: '', line: 0, column: 0 };\n    }\n    return tokens[pos];\n  }\n  \n  // SELECT\n  const selectToken = consume('keyword', 'SELECT');\n  \n  // Columns\n  const columns: string[] = [];\n  while (peek().type !== 'keyword' || peek().value !== 'FROM') {\n    if (peek().type === 'eof') {\n      throw new QueryError(`Expected FROM clause`);\n    }\n    \n    if (peek().type === 'identifier') {\n      columns.push(peek().value);\n      pos++;\n    } else if (peek().type === 'comma') {\n      if (columns.length === 0) {\n        throw new QueryError(`Empty column list`);\n      }\n      pos++; // consume comma\n    } else {\n      throw new QueryError(`Expected identifier or comma, got ${peek().type}`);\n    }\n    \n    // Check for trailing comma\n    if (peek().type === 'keyword' && peek().value === 'FROM') {\n      break;\n    }\n  }\n  \n  if (columns.length === 0) {\n    throw new QueryError(`Empty column list`);\n  }\n  \n  // FROM\n  consume('keyword', 'FROM');\n  const tableToken = consume('identifier');\n  const table = tableToken.value;\n  \n  let whereClause: WhereClause | undefined;\n  let orderByClause: OrderByClause | undefined;\n  let limitValue: number | undefined;\n  \n  // WHERE\n  if (peek().type === 'keyword' && peek().value === 'WHERE') {\n    pos++; // consume WHERE\n    const condition = parseCondition();\n    whereClause = { type: 'where', condition };\n  }\n  \n  // ORDER BY\n  if (peek().type === 'keyword' && peek().value === 'ORDER') {\n    pos++; // consume ORDER\n    consume('keyword', 'BY');\n    const columnToken = consume('identifier');\n    const column = columnToken.value;\n    \n    let direction: 'asc' | 'desc' = 'asc';\n    if (peek().type === 'keyword') {\n      if (peek().value === 'ASC') {\n        pos++;\n      } else if (peek().value === 'DESC') {\n        pos++;\n        direction = 'desc';\n      }\n    }\n    \n    orderByClause = { type: 'orderBy', column, direction };\n  }\n  \n  // LIMIT\n  if (peek().type === 'keyword' && peek().value === 'LIMIT') {\n    pos++; // consume LIMIT\n    const limitToken = consume('value');\n    const num = parseInt(limitToken.value);\n    if (isNaN(num) || num < 0) {\n      throw new QueryError(`Invalid LIMIT value: ${limitToken.value}`);\n    }\n    limitValue = num;\n  }\n  \n  // Check for unexpected tokens\n  if (peek().type !== 'eof') {\n    throw new QueryError(`Unexpected token after query: ${peek().value}`);\n  }\n  \n  return {\n    type: 'select',\n    columns,\n    table,\n    where: whereClause,\n    orderBy: orderByClause,\n    limit: limitValue\n  };\n}\n\nfunction parseCondition(): Condition {\n  return parseLogicalOr();\n}\n\nfunction parseLogicalOr(): Condition {\n  let left = parseLogicalAnd();\n  \n  while (peek().type === 'keyword' && peek().value === 'OR') {\n    const operatorToken = consume('keyword', 'OR');\n    const right = parseLogicalAnd();\n    left = { type: 'logical', left, operator: 'OR', right };\n  }\n  \n  return left;\n}\n\nfunction parseLogicalAnd(): Condition {\n  let left = parseComparison();\n  \n  while (peek().type === 'keyword' && peek().value === 'AND') {\n    const operatorToken = consume('keyword', 'AND');\n    const right = parseComparison();\n    left = { type: 'logical', left, operator: 'AND', right };\n  }\n  \n  return left;\n}\n\nfunction parseComparison(): Condition {\n  const leftToken = consume('identifier');\n  const left = leftToken.value;\n  \n  const opToken = consume('operator');\n  const op = opToken.value;\n  \n  if (!OPERATORS.has(op)) {\n    throw new QueryError(`Invalid operator: ${op}`);\n  }\n  \n  let rightValue: string | number;\n  const valueToken = peek();\n  if (valueToken.type === 'value') {\n    pos++;\n    if (valueToken.value.startsWith(\"'\")) {\n      // String literal\n      rightValue = valueToken.value.slice(1, -1); // Remove quotes\n    } else {\n      // Number literal\n      const num = parseInt(valueToken.value);\n      if (isNaN(num)) {\n        throw new QueryError(`Invalid number: ${valueToken.value}`);\n      }\n      rightValue = num;\n    }\n  } else {\n    throw new QueryError(`Expected value, got ${valueToken.type}`);\n  }\n  \n  return { type: 'comparison', left, operator: op, right: rightValue };\n}\n\nfunction evaluateCondition(row: Row, condition: Condition): boolean {\n  if (condition.type === 'comparison') {\n    const col = condition.left;\n    const op = condition.operator;\n    const value = condition.right;\n    \n    // If column doesn't exist in row, treat as non-match\n    if (!(col in row)) {\n      return op === '!=' ? true : false;\n    }\n    \n    const cellValue = row[col];\n    \n    // Type mismatch handling\n    if (typeof cellValue === 'number' && typeof value === 'string') {\n      return op === '!=' ? true : false;\n    }\n    if (typeof cellValue === 'string' && typeof value === 'number') {\n      return op === '!=' ? true : false;\n    }\n    \n    switch (op) {\n      case '=': return cellValue === value;\n      case '!=': return cellValue !== value;\n      case '<': return cellValue < value;\n      case '>': return cellValue > value;\n      case '<=': return cellValue <= value;\n      case '>=': return cellValue >= value;\n      default: return false;\n    }\n  } else if (condition.type === 'logical') {\n    const leftResult = evaluateCondition(row, condition.left);\n    const rightResult = evaluateCondition(row, condition.right);\n    \n    switch (condition.operator) {\n      case 'AND': return leftResult && rightResult;\n      case 'OR': return leftResult || rightResult;\n      default: return false;\n    }\n  }\n  \n  return false;\n}\n\nfunction sortRows(rows: Row[], orderBy: OrderByClause): Row[] {\n  const sorted = [...rows];\n  \n  return sorted.sort((a, b) => {\n    const col = orderBy.column;\n    \n    // If column doesn't exist in row, treat as equal\n    if (!(col in a) || !(col in b)) {\n      return 0;\n    }\n    \n    const aValue = a[col];\n    const bValue = b[col];\n    \n    // Type mismatch handling\n    if (typeof aValue === 'number' && typeof bValue === 'string') {\n      return 0;\n    }\n    if (typeof aValue === 'string' && typeof bValue === 'number') {\n      return 0;\n    }\n    \n    let result: number;\n    if (typeof aValue === 'number' && typeof bValue === 'number') {\n      result = aValue - bValue;\n    } else {\n      // Both are strings\n      result = (aValue as string).localeCompare(bValue as string);\n    }\n    \n    return orderBy.direction === 'asc' ? result : -result;\n  });\n}\n\nfunction projectRows(rows: Row[], columns: string[]): Row[] {\n  return rows.map(row => {\n    const newRow: Row = {};\n    for (const col of columns) {\n      if (col in row) {\n        newRow[col] = row[col];\n      }\n    }\n    return newRow;\n  });\n}\n\nexport function query(sql: string, rows: Row[]): Row[] {\n  try {\n    const tokens = tokenize(sql);\n    const ast = parse(tokens);\n    \n    // WHERE filtering\n    let filteredRows = rows;\n    if (ast.where) {\n      filteredRows = rows.filter(row => evaluateCondition(row, ast.where!.condition));\n    }\n    \n    // ORDER BY sorting\n    let sortedRows = filteredRows;\n    if (ast.orderBy) {\n      sortedRows = sortRows(filteredRows, ast.orderBy);\n    }\n    \n    // LIMIT truncation\n    let limitedRows = sortedRows;\n    if (ast.limit !== undefined) {\n      limitedRows = sortedRows.slice(0, ast.limit);\n    }\n    \n    // Column projection\n    let resultRows = limitedRows;\n    if (ast.columns[0] === '*') {\n      // Select all columns preserving original row structure\n      resultRows = limitedRows.map(row => ({ ...row }));\n    } else {\n      resultRows = projectRows(limitedRows, ast.columns);\n    }\n    \n    return resultRows;\n  } catch (error) {\n    if (error instanceof QueryError) {\n      throw error;\n    }\n    throw new QueryError(`Invalid query: ${error}`);\n  }\n}\n```",
    "passed": 7,
    "test_error": "mp/llmlab-ts-11-mini-sql-vm2whtrx/solution.test.ts:190:15)\n    Test.runInAsyncScope (node:async_hooks:227:14)\n    Test.run (node:internal/test_runner/test:1306:25)\n    Test.processPendingSubtests (node:internal/test_runner/test:897:18)\n    Test.postRun (node:internal/test_runner/test:1447:19)\n    Test.run (node:internal/test_runner/test:1372:12)\n    async Test.processPendingSubtests (node:internal/test_runner/test:897:7)\n  ...\n# Subtest: no WHERE returns all rows; whitespace is tolerated\nnot ok 19 - no WHERE returns all rows; whitespace is tolerated\n  ---\n  duration_ms: 0.02809\n  type: 'test'\n  location: '/tmp/llmlab-ts-11-mini-sql-vm2whtrx/solution.test.ts:1:5624'\n  failureType: 'testCodeFailure'\n  error: 'Unexpected character: *'\n  code: 'ERR_TEST_FAILURE'\n  stack: |-\n    tokenize (/tmp/llmlab-ts-11-mini-sql-vm2whtrx/solution.ts:124:11)\n    query (/tmp/llmlab-ts-11-mini-sql-vm2whtrx/solution.ts:402:20)\n    TestContext.<anonymous> (/tmp/llmlab-ts-11-mini-sql-vm2whtrx/solution.test.ts:203:16)\n    Test.runInAsyncScope (node:async_hooks:227:14)\n    Test.run (node:internal/test_runner/test:1306:25)\n    Test.processPendingSubtests (node:internal/test_runner/test:897:18)\n    Test.postRun (node:internal/test_runner/test:1447:19)\n    Test.run (node:internal/test_runner/test:1372:12)\n    async Test.processPendingSubtests (node:internal/test_runner/test:897:7)\n  ...\n# Subtest: throws: missing SELECT\nok 20 - throws: missing SELECT\n  ---\n  duration_ms: 0.211521\n  type: 'test'\n  ...\n# Subtest: throws: missing FROM\nok 21 - throws: missing FROM\n  ---\n  duration_ms: 0.06576\n  type: 'test'\n  ...\n# Subtest: throws: empty / malformed column list\nok 22 - throws: empty / malformed column list\n  ---\n  duration_ms: 0.05819\n  type: 'test'\n  ...\n# Subtest: throws: bad operator and malformed comparison\nok 23 - throws: bad operator and malformed comparison\n  ---\n  duration_ms: 0.075901\n  type: 'test'\n  ...\n# Subtest: throws: unterminated string literal\nok 24 - throws: unterminated string literal\n  ---\n  duration_ms: 0.04484\n  type: 'test'\n  ...\n# Subtest: throws: bad LIMIT (missing, negative, non-integer, string)\nok 25 - throws: bad LIMIT (missing, negative, non-integer, string)\n  ---\n  duration_ms: 0.492291\n  type: 'test'\n  ...\n# Subtest: throws: unknown clause / leftover tokens\nok 26 - throws: unknown clause / leftover tokens\n  ---\n  duration_ms: 0.072031\n  type: 'test'\n  ...\n1..26\n# tests 26\n# suites 0\n# pass 7\n# fail 19\n# cancelled 0\n# skipped 0\n# todo 0\n# duration_ms 85.067133"
  },
  {
    "total": 26,
    "answer": "Looking at the error, I see that the issue is in my tokenization logic. The problem is that when parsing `SELECT *`, the `*` character is being treated as an operator instead of a special identifier for \"all columns\". Let me fix this:\n\n```ts\nexport type Row = Record<string, number | string>;\n\nexport class QueryError extends Error {}\n\ntype Token = {\n  type: 'keyword' | 'identifier' | 'operator' | 'value' | 'comma' | 'eof';\n  value: string;\n  line: number;\n  column: number;\n};\n\ntype ASTNode =\n  | { type: 'select'; columns: string[]; table: string; where?: WhereClause; orderBy?: OrderByClause; limit?: number }\n  | { type: 'where'; condition: Condition }\n  | { type: 'condition'; left: string; operator: string; right: string | number }\n  | { type: 'orderBy'; column: string; direction: 'asc' | 'desc' }\n  | { type: 'limit'; count: number };\n\ntype WhereClause = {\n  type: 'where';\n  condition: Condition;\n};\n\ntype OrderByClause = {\n  type: 'orderBy';\n  column: string;\n  direction: 'asc' | 'desc';\n};\n\ntype Condition = \n  | { type: 'comparison'; left: string; operator: string; right: string | number }\n  | { type: 'logical'; left: Condition; operator: 'AND' | 'OR'; right: Condition };\n\nconst KEYWORDS = new Set(['SELECT', 'FROM', 'WHERE', 'ORDER', 'BY', 'ASC', 'DESC', 'LIMIT']);\nconst OPERATORS = new Set(['=', '!=', '<', '>', '<=', '>=']);\n\nfunction tokenize(sql: string): Token[] {\n  const tokens: Token[] = [];\n  let i = 0;\n  let line = 1;\n  let column = 0;\n\n  while (i < sql.length) {\n    const char = sql[i];\n    \n    if (char === ' ' || char === '\\t') {\n      i++;\n      column++;\n      continue;\n    }\n    \n    if (char === '\\n') {\n      line++;\n      column = 0;\n      i++;\n      continue;\n    }\n    \n    if (char === \"'\") {\n      // String literal\n      let j = i + 1;\n      let value = \"'\";\n      while (j < sql.length && sql[j] !== \"'\") {\n        value += sql[j];\n        j++;\n      }\n      if (j >= sql.length) {\n        throw new QueryError(`Unterminated string literal`);\n      }\n      value += \"'\";\n      tokens.push({ type: 'value', value, line, column });\n      i = j + 1;\n      column = j + 1;\n      continue;\n    }\n    \n    if (char === ',') {\n      tokens.push({ type: 'comma', value: ',', line, column });\n      i++;\n      column++;\n      continue;\n    }\n    \n    if (char === '*') {\n      // Special case for * in SELECT clause\n      tokens.push({ type: 'identifier', value: '*', line, column });\n      i++;\n      column++;\n      continue;\n    }\n    \n    if (/[a-zA-Z_]/.test(char)) {\n      // Identifier or keyword\n      let j = i;\n      while (j < sql.length && /[a-zA-Z0-9_]/.test(sql[j])) {\n        j++;\n      }\n      const value = sql.substring(i, j).toUpperCase();\n      tokens.push({ type: 'keyword', value, line, column });\n      i = j;\n      column = j;\n      continue;\n    }\n    \n    if (/[0-9]/.test(char)) {\n      // Number literal\n      let j = i;\n      while (j < sql.length && /[0-9]/.test(sql[j])) {\n        j++;\n      }\n      const value = sql.substring(i, j);\n      tokens.push({ type: 'value', value, line, column });\n      i = j;\n      column = j;\n      continue;\n    }\n    \n    if (['=', '<', '>'].includes(char)) {\n      // Operators\n      let j = i;\n      while (j < sql.length && ['=', '<', '>'].includes(sql[j])) {\n        j++;\n      }\n      const value = sql.substring(i, j);\n      tokens.push({ type: 'operator', value, line, column });\n      i = j;\n      column = j;\n      continue;\n    }\n    \n    // Unknown character\n    throw new QueryError(`Unexpected character: ${char}`);\n  }\n  \n  tokens.push({ type: 'eof', value: '', line, column });\n  return tokens;\n}\n\nfunction parse(tokens: Token[]): ASTNode {\n  let pos = 0;\n  \n  function consume(expectedType: string, expectedValue?: string): Token {\n    if (pos >= tokens.length) {\n      throw new QueryError(`Unexpected end of query`);\n    }\n    \n    const token = tokens[pos];\n    if (token.type !== expectedType || (expectedValue && token.value !== expectedValue)) {\n      throw new QueryError(`Expected ${expectedType} ${expectedValue ? `'${expectedValue}'` : ''}, got ${token.type} '${token.value}'`);\n    }\n    \n    pos++;\n    return token;\n  }\n  \n  function peek(): Token {\n    if (pos >= tokens.length) {\n      return { type: 'eof', value: '', line: 0, column: 0 };\n    }\n    return tokens[pos];\n  }\n  \n  // SELECT\n  const selectToken = consume('keyword', 'SELECT');\n  \n  // Columns\n  const columns: string[] = [];\n  while (peek().type !== 'keyword' || peek().value !== 'FROM') {\n    if (peek().type === 'eof') {\n      throw new QueryError(`Expected FROM clause`);\n    }\n    \n    if (peek().type === 'identifier') {\n      columns.push(peek().value);\n      pos++;\n    } else if (peek().type === 'comma') {\n      if (columns.length === 0) {\n        throw new QueryError(`Empty column list`);\n      }\n      pos++; // consume comma\n    } else {\n      throw new QueryError(`Expected identifier or comma, got ${peek().type}`);\n    }\n    \n    // Check for trailing comma\n    if (peek().type === 'keyword' && peek().value === 'FROM') {\n      break;\n    }\n  }\n  \n  if (columns.length === 0) {\n    throw new QueryError(`Empty column list`);\n  }\n  \n  // FROM\n  consume('keyword', 'FROM');\n  const tableToken = consume('identifier');\n  const table = tableToken.value;\n  \n  let whereClause: WhereClause | undefined;\n  let orderByClause: OrderByClause | undefined;\n  let limitValue: number | undefined;\n  \n  // WHERE\n  if (peek().type === 'keyword' && peek().value === 'WHERE') {\n    pos++; // consume WHERE\n    const condition = parseCondition();\n    whereClause = { type: 'where', condition };\n  }\n  \n  // ORDER BY\n  if (peek().type === 'keyword' && peek().value === 'ORDER') {\n    pos++; // consume ORDER\n    consume('keyword', 'BY');\n    const columnToken = consume('identifier');\n    const column = columnToken.value;\n    \n    let direction: 'asc' | 'desc' = 'asc';\n    if (peek().type === 'keyword') {\n      if (peek().value === 'ASC') {\n        pos++;\n      } else if (peek().value === 'DESC') {\n        pos++;\n        direction = 'desc';\n      }\n    }\n    \n    orderByClause = { type: 'orderBy', column, direction };\n  }\n  \n  // LIMIT\n  if (peek().type === 'keyword' && peek().value === 'LIMIT') {\n    pos++; // consume LIMIT\n    const limitToken = consume('value');\n    const num = parseInt(limitToken.value);\n    if (isNaN(num) || num < 0) {\n      throw new QueryError(`Invalid LIMIT value: ${limitToken.value}`);\n    }\n    limitValue = num;\n  }\n  \n  // Check for unexpected tokens\n  if (peek().type !== 'eof') {\n    throw new QueryError(`Unexpected token after query: ${peek().value}`);\n  }\n  \n  return {\n    type: 'select',\n    columns,\n    table,\n    where: whereClause,\n    orderBy: orderByClause,\n    limit: limitValue\n  };\n}\n\nfunction parseCondition(): Condition {\n  return parseLogicalOr();\n}\n\nfunction parseLogicalOr(): Condition {\n  let left = parseLogicalAnd();\n  \n  while (peek().type === 'keyword' && peek().value === 'OR') {\n    const operatorToken = consume('keyword', 'OR');\n    const right = parseLogicalAnd();\n    left = { type: 'logical', left, operator: 'OR', right };\n  }\n  \n  return left;\n}\n\nfunction parseLogicalAnd(): Condition {\n  let left = parseComparison();\n  \n  while (peek().type === 'keyword' && peek().value === 'AND') {\n    const operatorToken = consume('keyword', 'AND');\n    const right = parseComparison();\n    left = { type: 'logical', left, operator: 'AND', right };\n  }\n  \n  return left;\n}\n\nfunction parseComparison(): Condition {\n  const leftToken = consume('identifier');\n  const left = leftToken.value;\n  \n  const opToken = consume('operator');\n  const op = opToken.value;\n  \n  if (!OPERATORS.has(op)) {\n    throw new QueryError(`Invalid operator: ${op}`);\n  }\n  \n  let rightValue: string | number;\n  const valueToken = peek();\n  if (valueToken.type === 'value') {\n    pos++;\n    if (valueToken.value.startsWith(\"'\")) {\n      // String literal\n      rightValue = valueToken.value.slice(1, -1); // Remove quotes\n    } else {\n      // Number literal\n      const num = parseInt(valueToken.value);\n      if (isNaN(num)) {\n        throw new QueryError(`Invalid number: ${valueToken.value}`);\n      }\n      rightValue = num;\n    }\n  } else {\n    throw new QueryError(`Expected value, got ${valueToken.type}`);\n  }\n  \n  return { type: 'comparison', left, operator: op, right: rightValue };\n}\n\nfunction evaluateCondition(row: Row, condition: Condition): boolean {\n  if (condition.type === 'comparison') {\n    const col = condition.left;\n    const op = condition.operator;\n    const value = condition.right;\n    \n    // If column doesn't exist in row, treat as non-match\n    if (!(col in row)) {\n      return op === '!=' ? true : false;\n    }\n    \n    const cellValue = row[col];\n    \n    // Type mismatch handling\n    if (typeof cellValue === 'number' && typeof value === 'string') {\n      return op === '!=' ? true : false;\n    }\n    if (typeof cellValue === 'string' && typeof value === 'number') {\n      return op === '!=' ? true : false;\n    }\n    \n    switch (op) {\n      case '=': return cellValue === value;\n      case '!=': return cellValue !== value;\n      case '<': return cellValue < value;\n      case '>': return cellValue > value;\n      case '<=': return cellValue <= value;\n      case '>=': return cellValue >= value;\n      default: return false;\n    }\n  } else if (condition.type === 'logical') {\n    const leftResult = evaluateCondition(row, condition.left);\n    const rightResult = evaluateCondition(row, condition.right);\n    \n    switch (condition.operator) {\n      case 'AND': return leftResult && rightResult;\n      case 'OR': return leftResult || rightResult;\n      default: return false;\n    }\n  }\n  \n  return false;\n}\n\nfunction sortRows(rows: Row[], orderBy: OrderByClause): Row[] {\n  const sorted = [...rows];\n  \n  return sorted.sort((a, b) => {\n    const col = orderBy.column;\n    \n    // If column doesn't exist in row, treat as equal\n    if (!(col in a) || !(col in b)) {\n      return 0;\n    }\n    \n    const aValue = a[col];\n    const bValue = b[col];\n    \n    // Type mismatch handling\n    if (typeof aValue === 'number' && typeof bValue === 'string') {\n      return 0;\n    }\n    if (typeof aValue === 'string' && typeof bValue === 'number') {\n      return 0;\n    }\n    \n    let result: number;\n    if (typeof aValue === 'number' && typeof bValue === 'number') {\n      result = aValue - bValue;\n    } else {\n      // Both are strings\n      result = (aValue as string).localeCompare(bValue as string);\n    }\n    \n    return orderBy.direction === 'asc' ? result : -result;\n  });\n}\n\nfunction projectRows(rows: Row[], columns: string[]): Row[] {\n  return rows.map(row => {\n    const newRow: Row = {};\n    for (const col of columns) {\n      if (col in row) {\n        newRow[col] = row[col];\n      }\n    }\n    return newRow;\n  });\n}\n\nexport function query(sql: string, rows: Row[]): Row[] {\n  try {\n    const tokens = tokenize(sql);\n    const ast = parse(tokens);\n    \n    // WHERE filtering\n    let filteredRows = rows;\n    if (ast.where) {\n      filteredRows = rows.filter(row => evaluateCondition(row, ast.where!.condition));\n    }\n    \n    // ORDER BY sorting\n    let sortedRows = filteredRows;\n    if (ast.orderBy) {\n      sortedRows = sortRows(filteredRows, ast.orderBy);\n    }\n    \n    // LIMIT truncation\n    let limitedRows = sortedRows;\n    if (ast.limit !== undefined) {\n      limitedRows = sortedRows.slice(0, ast.limit);\n    }\n    \n    // Column projection\n    let resultRows = limitedRows;\n    if (ast.columns[0] === '*') {\n      // Select all columns preserving original row structure\n      resultRows = limitedRows.map(row => ({ ...row }));\n    } else {\n      resultRows = projectRows(limitedRows, ast.columns);\n    }\n    \n    return resultRows;\n  } catch (error) {\n    if (error instanceof QueryError) {\n      throw error;\n    }\n    throw new QueryError(`Invalid query: ${error}`);\n  }\n}\n```",
    "passed": 7,
    "test_error": "Scope (node:async_hooks:227:14)\n    Test.run (node:internal/test_runner/test:1306:25)\n    Test.processPendingSubtests (node:internal/test_runner/test:897:18)\n    Test.postRun (node:internal/test_runner/test:1447:19)\n    Test.run (node:internal/test_runner/test:1372:12)\n    async Test.processPendingSubtests (node:internal/test_runner/test:897:7)\n  ...\n# Subtest: no WHERE returns all rows; whitespace is tolerated\nnot ok 19 - no WHERE returns all rows; whitespace is tolerated\n  ---\n  duration_ms: 0.02946\n  type: 'test'\n  location: '/tmp/llmlab-ts-11-mini-sql-155jziy5/solution.test.ts:1:5624'\n  failureType: 'testCodeFailure'\n  error: \"Expected identifier , got keyword 'T'\"\n  code: 'ERR_TEST_FAILURE'\n  stack: |-\n    consume (/tmp/llmlab-ts-11-mini-sql-155jziy5/solution.ts:149:13)\n    parse (/tmp/llmlab-ts-11-mini-sql-155jziy5/solution.ts:197:22)\n    query (/tmp/llmlab-ts-11-mini-sql-155jziy5/solution.ts:411:17)\n    TestContext.<anonymous> (/tmp/llmlab-ts-11-mini-sql-155jziy5/solution.test.ts:203:16)\n    Test.runInAsyncScope (node:async_hooks:227:14)\n    Test.run (node:internal/test_runner/test:1306:25)\n    Test.processPendingSubtests (node:internal/test_runner/test:897:18)\n    Test.postRun (node:internal/test_runner/test:1447:19)\n    Test.run (node:internal/test_runner/test:1372:12)\n    async Test.processPendingSubtests (node:internal/test_runner/test:897:7)\n  ...\n# Subtest: throws: missing SELECT\nok 20 - throws: missing SELECT\n  ---\n  duration_ms: 0.201391\n  type: 'test'\n  ...\n# Subtest: throws: missing FROM\nok 21 - throws: missing FROM\n  ---\n  duration_ms: 0.05843\n  type: 'test'\n  ...\n# Subtest: throws: empty / malformed column list\nok 22 - throws: empty / malformed column list\n  ---\n  duration_ms: 0.05029\n  type: 'test'\n  ...\n# Subtest: throws: bad operator and malformed comparison\nok 23 - throws: bad operator and malformed comparison\n  ---\n  duration_ms: 0.484502\n  type: 'test'\n  ...\n# Subtest: throws: unterminated string literal\nok 24 - throws: unterminated string literal\n  ---\n  duration_ms: 0.0533\n  type: 'test'\n  ...\n# Subtest: throws: bad LIMIT (missing, negative, non-integer, string)\nok 25 - throws: bad LIMIT (missing, negative, non-integer, string)\n  ---\n  duration_ms: 0.05638\n  type: 'test'\n  ...\n# Subtest: throws: unknown clause / leftover tokens\nok 26 - throws: unknown clause / leftover tokens\n  ---\n  duration_ms: 0.053021\n  type: 'test'\n  ...\n1..26\n# tests 26\n# suites 0\n# pass 7\n# fail 19\n# cancelled 0\n# skipped 0\n# todo 0\n# duration_ms 89.022646"
  },
  {
    "total": 26,
    "answer": "Looking at the error, I see there's an issue with how I'm handling tokens. The problem is in my parsing logic - when I encounter `SELECT *`, I'm treating `*` as an identifier but then trying to parse it as a column name which causes issues later.\n\nLet me restructure this properly:\n\n```ts\nexport type Row = Record<string, number | string>;\n\nexport class QueryError extends Error {}\n\ntype Token = {\n  type: 'keyword' | 'identifier' | 'operator' | 'value' | 'comma' | 'eof';\n  value: string;\n  line: number;\n  column: number;\n};\n\ntype ASTNode =\n  | { type: 'select'; columns: string[]; table: string; where?: WhereClause; orderBy?: OrderByClause; limit?: number }\n  | { type: 'where'; condition: Condition }\n  | { type: 'condition'; left: string; operator: string; right: string | number }\n  | { type: 'orderBy'; column: string; direction: 'asc' | 'desc' }\n  | { type: 'limit'; count: number };\n\ntype WhereClause = {\n  type: 'where';\n  condition: Condition;\n};\n\ntype OrderByClause = {\n  type: 'orderBy';\n  column: string;\n  direction: 'asc' | 'desc';\n};\n\ntype Condition = \n  | { type: 'comparison'; left: string; operator: string; right: string | number }\n  | { type: 'logical'; left: Condition; operator: 'AND' | 'OR'; right: Condition };\n\nconst KEYWORDS = new Set(['SELECT', 'FROM', 'WHERE', 'ORDER', 'BY', 'ASC', 'DESC', 'LIMIT']);\nconst OPERATORS = new Set(['=', '!=', '<', '>', '<=', '>=']);\n\nfunction tokenize(sql: string): Token[] {\n  const tokens: Token[] = [];\n  let i = 0;\n  let line = 1;\n  let column = 0;\n\n  while (i < sql.length) {\n    const char = sql[i];\n    \n    if (char === ' ' || char === '\\t') {\n      i++;\n      column++;\n      continue;\n    }\n    \n    if (char === '\\n') {\n      line++;\n      column = 0;\n      i++;\n      continue;\n    }\n    \n    if (char === \"'\") {\n      // String literal\n      let j = i + 1;\n      let value = \"'\";\n      while (j < sql.length && sql[j] !== \"'\") {\n        value += sql[j];\n        j++;\n      }\n      if (j >= sql.length) {\n        throw new QueryError(`Unterminated string literal`);\n      }\n      value += \"'\";\n      tokens.push({ type: 'value', value, line, column });\n      i = j + 1;\n      column = j + 1;\n      continue;\n    }\n    \n    if (char === ',') {\n      tokens.push({ type: 'comma', value: ',', line, column });\n      i++;\n      column++;\n      continue;\n    }\n    \n    if (char === '*') {\n      // Special case for * in SELECT clause\n      tokens.push({ type: 'identifier', value: '*', line, column });\n      i++;\n      column++;\n      continue;\n    }\n    \n    if (/[a-zA-Z_]/.test(char)) {\n      // Identifier or keyword\n      let j = i;\n      while (j < sql.length && /[a-zA-Z0-9_]/.test(sql[j])) {\n        j++;\n      }\n      const value = sql.substring(i, j).toUpperCase();\n      tokens.push({ type: 'keyword', value, line, column });\n      i = j;\n      column = j;\n      continue;\n    }\n    \n    if (/[0-9]/.test(char)) {\n      // Number literal\n      let j = i;\n      while (j < sql.length && /[0-9]/.test(sql[j])) {\n        j++;\n      }\n      const value = sql.substring(i, j);\n      tokens.push({ type: 'value', value, line, column });\n      i = j;\n      column = j;\n      continue;\n    }\n    \n    if (['=', '<', '>'].includes(char)) {\n      // Operators\n      let j = i;\n      while (j < sql.length && ['=', '<', '>'].includes(sql[j])) {\n        j++;\n      }\n      const value = sql.substring(i, j);\n      tokens.push({ type: 'operator', value, line, column });\n      i = j;\n      column = j;\n      continue;\n    }\n    \n    // Unknown character\n    throw new QueryError(`Unexpected character: ${char}`);\n  }\n  \n  tokens.push({ type: 'eof', value: '', line, column });\n  return tokens;\n}\n\nfunction parse(tokens: Token[]): ASTNode {\n  let pos = 0;\n  \n  function consume(expectedType: string, expectedValue?: string): Token {\n    if (pos >= tokens.length) {\n      throw new QueryError(`Unexpected end of query`);\n    }\n    \n    const token = tokens[pos];\n    if (token.type !== expectedType || (expectedValue && token.value !== expectedValue)) {\n      throw new QueryError(`Expected ${expectedType} ${expectedValue ? `'${expectedValue}'` : ''}, got ${token.type} '${token.value}'`);\n    }\n    \n    pos++;\n    return token;\n  }\n  \n  function peek(): Token {\n    if (pos >= tokens.length) {\n      return { type: 'eof', value: '', line: 0, column: 0 };\n    }\n    return tokens[pos];\n  }\n  \n  // SELECT\n  const selectToken = consume('keyword', 'SELECT');\n  \n  // Columns - handle special case for *\n  const columns: string[] = [];\n  let firstColumn = true;\n  \n  while (peek().type !== 'keyword' || peek().value !== 'FROM') {\n    if (peek().type === 'eof') {\n      throw new QueryError(`Expected FROM clause`);\n    }\n    \n    if (peek().type === 'identifier') {\n      columns.push(peek().value);\n      pos++;\n    } else if (peek().type === 'comma') {\n      if (columns.length === 0) {\n        throw new QueryError(`Empty column list`);\n      }\n      pos++; // consume comma\n    } else {\n      throw new QueryError(`Expected identifier or comma, got ${peek().type}`);\n    }\n    \n    // Check for trailing comma\n    if (peek().type === 'keyword' && peek().value === 'FROM') {\n      break;\n    }\n  }\n  \n  if (columns.length === 0) {\n    throw new QueryError(`Empty column list`);\n  }\n  \n  // FROM\n  consume('keyword', 'FROM');\n  const tableToken = consume('identifier');\n  const table = tableToken.value;\n  \n  let whereClause: WhereClause | undefined;\n  let orderByClause: OrderByClause | undefined;\n  let limitValue: number | undefined;\n  \n  // WHERE\n  if (peek().type === 'keyword' && peek().value === 'WHERE') {\n    pos++; // consume WHERE\n    const condition = parseCondition();\n    whereClause = { type: 'where', condition };\n  }\n  \n  // ORDER BY\n  if (peek().type === 'keyword' && peek().value === 'ORDER') {\n    pos++; // consume ORDER\n    consume('keyword', 'BY');\n    const columnToken = consume('identifier');\n    const column = columnToken.value;\n    \n    let direction: 'asc' | 'desc' = 'asc';\n    if (peek().type === 'keyword') {\n      if (peek().value === 'ASC') {\n        pos++;\n      } else if (peek().value === 'DESC') {\n        pos++;\n        direction = 'desc';\n      }\n    }\n    \n    orderByClause = { type: 'orderBy', column, direction };\n  }\n  \n  // LIMIT\n  if (peek().type === 'keyword' && peek().value === 'LIMIT') {\n    pos++; // consume LIMIT\n    const limitToken = consume('value');\n    const num = parseInt(limitToken.value);\n    if (isNaN(num) || num < 0) {\n      throw new QueryError(`Invalid LIMIT value: ${limitToken.value}`);\n    }\n    limitValue = num;\n  }\n  \n  // Check for unexpected tokens\n  if (peek().type !== 'eof') {\n    throw new QueryError(`Unexpected token after query: ${peek().value}`);\n  }\n  \n  return {\n    type: 'select',\n    columns,\n    table,\n    where: whereClause,\n    orderBy: orderByClause,\n    limit: limitValue\n  };\n}\n\nfunction parseCondition(): Condition {\n  return parseLogicalOr();\n}\n\nfunction parseLogicalOr(): Condition {\n  let left = parseLogicalAnd();\n  \n  while (peek().type === 'keyword' && peek().value === 'OR') {\n    const operatorToken = consume('keyword', 'OR');\n    const right = parseLogicalAnd();\n    left = { type: 'logical', left, operator: 'OR', right };\n  }\n  \n  return left;\n}\n\nfunction parseLogicalAnd(): Condition {\n  let left = parseComparison();\n  \n  while (peek().type === 'keyword' && peek().value === 'AND') {\n    const operatorToken = consume('keyword', 'AND');\n    const right = parseComparison();\n    left = { type: 'logical', left, operator: 'AND', right };\n  }\n  \n  return left;\n}\n\nfunction parseComparison(): Condition {\n  const leftToken = consume('identifier');\n  const left = leftToken.value;\n  \n  const opToken = consume('operator');\n  const op = opToken.value;\n  \n  if (!OPERATORS.has(op)) {\n    throw new QueryError(`Invalid operator: ${op}`);\n  }\n  \n  let rightValue: string | number;\n  const valueToken = peek();\n  if (valueToken.type === 'value') {\n    pos++;\n    if (valueToken.value.startsWith(\"'\")) {\n      // String literal\n      rightValue = valueToken.value.slice(1, -1); // Remove quotes\n    } else {\n      // Number literal\n      const num = parseInt(valueToken.value);\n      if (isNaN(num)) {\n        throw new QueryError(`Invalid number: ${valueToken.value}`);\n      }\n      rightValue = num;\n    }\n  } else {\n    throw new QueryError(`Expected value, got ${valueToken.type}`);\n  }\n  \n  return { type: 'comparison', left, operator: op, right: rightValue };\n}\n\nfunction evaluateCondition(row: Row, condition: Condition): boolean {\n  if (condition.type === 'comparison') {\n    const col = condition.left;\n    const op = condition.operator;\n    const value = condition.right;\n    \n    // If column doesn't exist in row, treat as non-match\n    if (!(col in row)) {\n      return op === '!=' ? true : false;\n    }\n    \n    const cellValue = row[col];\n    \n    // Type mismatch handling\n    if (typeof cellValue === 'number' && typeof value === 'string') {\n      return op === '!=' ? true : false;\n    }\n    if (typeof cellValue === 'string' && typeof value === 'number') {\n      return op === '!=' ? true : false;\n    }\n    \n    switch (op) {\n      case '=': return cellValue === value;\n      case '!=': return cellValue !== value;\n      case '<': return cellValue < value;\n      case '>': return cellValue > value;\n      case '<=': return cellValue <= value;\n      case '>=': return cellValue >= value;\n      default: return false;\n    }\n  } else if (condition.type === 'logical') {\n    const leftResult = evaluateCondition(row, condition.left);\n    const rightResult = evaluateCondition(row, condition.right);\n    \n    switch (condition.operator) {\n      case 'AND': return leftResult && rightResult;\n      case 'OR': return leftResult || rightResult;\n      default: return false;\n    }\n  }\n  \n  return false;\n}\n\nfunction sortRows(rows: Row[], orderBy: OrderByClause): Row[] {\n  const sorted = [...rows];\n  \n  return sorted.sort((a, b) => {\n    const col = orderBy.column;\n    \n    // If column doesn't exist in row, treat as equal\n    if (!(col in a) || !(col in b)) {\n      return 0;\n    }\n    \n    const aValue = a[col];\n    const bValue = b[col];\n    \n    // Type mismatch handling\n    if (typeof aValue === 'number' && typeof bValue === 'string') {\n      return 0;\n    }\n    if (typeof aValue === 'string' && typeof bValue === 'number') {\n      return 0;\n    }\n    \n    let result: number;\n    if (typeof aValue === 'number' && typeof bValue === 'number') {\n      result = aValue - bValue;\n    } else {\n      // Both are strings\n      result = (aValue as string).localeCompare(bValue as string);\n    }\n    \n    return orderBy.direction === 'asc' ? result : -result;\n  });\n}\n\nfunction projectRows(rows: Row[], columns: string[]): Row[] {\n  return rows.map(row => {\n    const newRow: Row = {};\n    for (const col of columns) {\n      if (col in row) {\n        newRow[col] = row[col];\n      }\n    }\n    return newRow;\n  });\n}\n\nexport function query(sql: string, rows: Row[]): Row[] {\n  try {\n    const tokens = tokenize(sql);\n    const ast = parse(tokens);\n    \n    // WHERE filtering\n    let filteredRows = rows;\n    if (ast.where) {\n      filteredRows = rows.filter(row => evaluateCondition(row, ast.where!.condition));\n    }\n    \n    // ORDER BY sorting\n    let sortedRows = filteredRows;\n    if (ast.orderBy) {\n      sortedRows = sortRows(filteredRows, ast.orderBy);\n    }\n    \n    // LIMIT truncation\n    let limitedRows = sortedRows;\n    if (ast.limit !== undefined) {\n      limitedRows = sortedRows.slice(0, ast.limit);\n    }\n    \n    // Column projection\n    let resultRows = limitedRows;\n    if (ast.columns[0] === '*') {\n      // Select all columns preserving original row structure\n      resultRows = limitedRows.map(row => ({ ...row }));\n    } else {\n      resultRows = projectRows(limitedRows, ast.columns);\n    }\n    \n    return resultRows;\n  } catch (error) {\n    if (error instanceof QueryError) {\n      throw error;\n    }\n    throw new QueryError(`Invalid query: ${error}`);\n  }\n}\n```",
    "passed": 7,
    "test_error": ""
  }
]