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**Node.js:**

```javascript
const Database = require('better-sqlite3');

function querySQLiteToJSON(dbPath, query) {
  const db = new Database(dbPath, { readonly: true });
  const rows = db.prepare(query).all();
  db.close();
  return rows;
}

// Usage
// const users = querySQLiteToJSON('./database.db', 'SELECT * FROM users LIMIT 10');
// console.log(JSON.stringify(users, null, 2));

undefined

**Node.js:**

```javascript
const Database = require('better-sqlite3');
const fs = require('fs');

function querySQLiteToCSV(dbPath, query, outputPath) {
  const db = new Database(dbPath, { readonly: true });
  const rows = db.prepare(query).all();
  db.close();
  
  if (rows.length === 0) {
    return 'No results';
  }
  
  // Generate CSV
  const headers = Object.keys(rows[0]).join(',');
  const csvRows = rows.map(row => 
    Object.values(row).map(val => 
      typeof val === 'string' && val.includes(',') ? `"${val}"` : val
    ).join(',')
  );
  
  const csv = [headers, ...csvRows].join('\n');
  
  if (outputPath) {
    fs.writeFileSync(outputPath, csv);
    return `Exported ${rows.length} rows to ${outputPath}`;
  }
  
  return csv;
}

// Usage
// querySQLiteToCSV('./database.db', 'SELECT * FROM users LIMIT 10', './users.csv');

undefined

**Node.js:**

```javascript
const { Pool } = require('pg');

async function queryPostgreSQL(connectionString, query) {
  const pool = new Pool({ connectionString });
  
  try {
    const result = await pool.query(query);
    return result.rows;
  } finally {
    await pool.end();
  }
}

// Usage
// const connStr = 'postgresql://user:password@localhost:5432/mydb';
// queryPostgreSQL(connStr, 'SELECT * FROM users LIMIT 10')
//   .then(rows => console.log(JSON.stringify(rows, null, 2)));

undefined

**Node.js:**

```javascript
const mysql = require('mysql2/promise');

async function queryMySQL(config, query) {
  const connection = await mysql.createConnection({
    host: config.host || 'localhost',
    user: config.user,
    password: config.password,
    database: config.database,
    connectTimeout: 10000
  });
  
  try {
    const [rows] = await connection.execute(query);
    return rows;
  } finally {
    await connection.end();
  }
}

// Usage
// const config = {
//   host: 'localhost',
//   user: 'root',
//   password: 'mypassword',
//   database: 'mydb'
// };
// queryMySQL(config, 'SELECT * FROM users LIMIT 10')
//   .then(rows => console.log(JSON.stringify(rows, null, 2)));

#!/bin/bash
DB_PATH="database.db"
QUERY="SELECT * FROM users WHERE active=1;"
OUTPUT_FILE="users.csv"

**Node.js:**

```javascript
const Database = require('better-sqlite3');
const fs = require('fs');

async function exportSQLiteWithValidation(options) {
  const { dbPath, query, outputPath, format = 'json' } = options;
  
  // Validate database exists
  if (!fs.existsSync(dbPath)) {
    throw new Error(`Database file not found: ${dbPath}`);
  }
  
  let db;
  try {
    db = new Database(dbPath, { readonly: true, timeout: 10000 });
    
    // Prepare and execute query
    const stmt = db.prepare(query);
    const rows = stmt.all();
    
    if (rows.length === 0) {
      return { success: true, rowCount: 0, message: 'No rows returned' };
    }
    
    // Export based on format
    let output;
    if (format === 'json') {
      output = JSON.stringify(rows, null, 2);
    } else if (format === 'csv') {
      const headers = Object.keys(rows[0]).join(',');
      const csvRows = rows.map(row => 
        Object.values(row).map(val => 
          typeof val === 'string' && val.includes(',') ? `"${val.replace(/"/g, '""')}"` : val
        ).join(',')
      );
      output = [headers, ...csvRows].join('\n');
    } else {
      throw new Error(`Unsupported format: ${format}`);
    }
    
    // Write to file
    fs.writeFileSync(outputPath, output);
    
    return {
      success: true,
      rowCount: rows.length,
      outputPath,
      format,
      message: `Exported ${rows.length} rows to ${outputPath}`
    };
    
  } catch (err) {
    throw new Error(`Database export failed: ${err.message}`);
  } finally {
    if (db) db.close();
  }
}

// Usage
// exportSQLiteWithValidation({
//   dbPath: './database.db',
//   query: 'SELECT * FROM users WHERE active=1',
//   outputPath: './users.json',
//   format: 'json'
// }).then(result => console.log(result));

You have database query and export capability. When a user asks to query a database:

1. Identify the database type (SQLite, PostgreSQL, MySQL) from:
   - File extension (.db, .sqlite, .sqlite3 = SQLite)
   - Connection string (postgresql://, mysql://)
   - User specification

2. For SQLite:
   - Use `sqlite3 database.db "QUERY" -json` for JSON output
   - Use `.mode csv` with `.headers on` for CSV output
   - Always check if the database file exists first

3. For PostgreSQL:
   - Use `psql` with connection string or environment variables
   - Use `COPY ... TO STDOUT WITH CSV HEADER` for CSV export
   - Export JSON using `row_to_json()` function

4. For MySQL:
   - Use `mysql` with `-e` flag for queries
   - Use `--batch --silent` for CSV-like output
   - Set connection timeout with `--connect-timeout=10`

5. Always:
   - Validate database/table exists before querying
   - Use readonly connections when only reading
   - Handle errors gracefully with clear messages
   - Sanitize outputs (escape commas in CSV, quote strings)

6. For large datasets:
   - Add LIMIT clause to queries
   - Use pagination with OFFSET for very large tables
   - Warn user if result set is likely to be huge