Query Operations

/**
 * Execute a SQL query asynchronously
 * @param text - SQL query text
 * @param callback - Callback function receiving results
 */
client.query(
  text: string, 
  callback: (err: Error | null, rows: any[], results?: QueryResult | QueryResult[]) => void
): void;

/**
 * Execute a parameterized SQL query asynchronously
 * @param text - SQL query text with $1, $2, etc. placeholders
 * @param values - Array of parameter values
 * @param callback - Callback function receiving results
 */
client.query(
  text: string,
  values: any[],
  callback: (err: Error | null, rows: any[], results?: QueryResult | QueryResult[]) => void
): void;

const client = new Client();
client.connectSync();

// Simple text query
client.query('SELECT NOW() AS current_time', function(err, rows) {
  if (err) throw err;
  console.log('Current time:', rows[0].current_time);
});

// Parameterized query for safety
client.query(
  'SELECT * FROM users WHERE age > $1 AND city = $2',
  [25, 'New York'],
  function(err, rows) {
    if (err) throw err;
    console.log('Found users:', rows);
  }
);

// Query with multiple result sets
client.query(
  'SELECT 1 as first; SELECT 2 as second',
  function(err, rows, results) {
    if (err) throw err;
    console.log('Multiple results:', results);
    // rows will be an array of arrays: [[{first: 1}], [{second: 2}]]
    // results will be an array of QueryResult objects
  }
);

/**
 * Execute a SQL query synchronously
 * @param text - SQL query text
 * @param values - Optional array of parameter values
 * @returns Array of result rows
 * @throws Error if query fails
 */
client.querySync(text: string, values?: any[]): any[];

const client = new Client();
client.connectSync();

try {
  // Simple text query
  const rows = client.querySync('SELECT NOW() AS current_time');
  console.log('Current time:', rows[0].current_time);

  // Parameterized query
  const users = client.querySync(
    'SELECT name, email FROM users WHERE age > $1',
    [25]
  );
  console.log('Users over 25:', users);

  // Data modification query
  const insertResult = client.querySync(
    'INSERT INTO logs (message, created_at) VALUES ($1, NOW()) RETURNING id',
    ['Application started']
  );
  console.log('Inserted log ID:', insertResult[0].id);

} catch (err) {
  console.error('Query failed:', err.message);
}

// Default object mode results
interface QueryResultRow {
  [columnName: string]: any;
}

// Array mode results (when arrayMode: true in constructor)
type QueryResultRowArray = any[];

const client = new Client();
const rows = client.querySync('SELECT id, name, age FROM users LIMIT 2');
console.log(rows);
// [
//   { id: 1, name: 'Alice', age: 30 },
//   { id: 2, name: 'Bob', age: 25 }
// ]

const client = new Client({ arrayMode: true });
const rows = client.querySync('SELECT id, name, age FROM users LIMIT 2');
console.log(rows);
// [
//   [1, 'Alice', 30],
//   [2, 'Bob', 25]
// ]

/**
 * Cancel the currently executing query
 * @param callback - Required callback function
 */
client.cancel(callback: (err: Error | null) => void): void;

const client = new Client();
client.connectSync();

// Start a long-running query
client.query('SELECT pg_sleep(60)', function(err, rows) {
  if (err) {
    console.log('Query was cancelled:', err.message);
  } else {
    console.log('Query completed');
  }
});

// Cancel it after 1 second
setTimeout(function() {
  client.cancel(function(err) {
    if (err) {
      console.error('Cancel failed:', err.message);
    } else {
      console.log('Cancel request sent');
    }
  });
}, 1000);

/**
 * Escape a string literal for safe inclusion in SQL
 * @param value - String value to escape
 * @returns Escaped string literal with quotes
 */
client.escapeLiteral(value: string): string;

/**
 * Escape an identifier for safe inclusion in SQL
 * @param value - Identifier to escape
 * @returns Escaped identifier with quotes if needed
 */
client.escapeIdentifier(value: string): string;

const client = new Client();
client.connectSync();

const userInput = "Robert'; DROP TABLE students; --";
const tableName = "user data";

// Escape string literal
const escapedValue = client.escapeLiteral(userInput);
console.log(escapedValue); // 'Robert''; DROP TABLE students; --'

// Escape identifier
const escapedTable = client.escapeIdentifier(tableName);
console.log(escapedTable); // "user data"

// Use in queries (although parameterized queries are preferred)
const query = `SELECT * FROM ${escapedTable} WHERE name = ${escapedValue}`;

// Async error handling
client.query('INVALID SQL', function(err, rows) {
  if (err) {
    console.error('Query error:', err.message);
    // err.message contains PostgreSQL error details
  }
});

// Sync error handling
try {
  client.querySync('INVALID SQL');
} catch (err) {
  console.error('Query error:', err.message);
  // err.message contains PostgreSQL error details
}