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MySQL2

MySQL client for Node.js with focus on performance. Supports prepared statements, non-utf8 encodings, binary log protocol, compression, ssl much more.

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Installationโ€‹

MySQL2 is free from native bindings and can be installed on Linux, Mac OS or Windows without any issues.

npm install --save mysql2

First Queryโ€‹

To explore more queries examples, please visit the example sections Simple Queries and Prepared Statements.

// Get the client
import mysql from 'mysql2/promise';

// Create the connection to database
const connection = await mysql.createConnection({
  host: 'localhost',
  user: 'root',
  database: 'test',
});

// A simple SELECT query
try {
  const [results, fields] = await connection.query(
    'SELECT * FROM `table` WHERE `name` = "Page" AND `age` > 45'
  );

  console.log(results); // results contains rows returned by server
  console.log(fields); // fields contains extra meta data about results, if available
} catch (err) {
  console.log(err);
}

// Using placeholders
try {
  const [results] = await connection.query(
    'SELECT * FROM `table` WHERE `name` = ? AND `age` > ?',
    ['Page', 45]
  );

  console.log(results);
} catch (err) {
  console.log(err);
}

Using Prepared Statementsโ€‹

With MySQL2 you also get the prepared statements. With prepared statements MySQL doesn't have to prepare plan for same query every time, this results in better performance. If you don't know why they are important, please check these discussions:

MySQL2 provides execute helper which will prepare and query the statement. You can also manually prepare / unprepare statement with prepare / unprepare methods.

To explore more Prepared Statements and Placeholders examples, please visit the example section Prepared Statements.

import mysql from 'mysql2/promise';

try {
  // create the connection to database
  const connection = await mysql.createConnection({
    host: 'localhost',
    user: 'root',
    database: 'test',
  });

  // execute will internally call prepare and query
  const [results, fields] = await connection.execute(
    'SELECT * FROM `table` WHERE `name` = ? AND `age` > ?',
    ['Rick C-137', 53]
  );

  console.log(results); // results contains rows returned by server
  console.log(fields); // fields contains extra meta data about results, if available
} catch (err) {
  console.log(err);
}
tip

If you execute same statement again, it will be picked from a LRU cache which will save query preparation time and give better performance.

Using Connection Poolsโ€‹

Connection pools help reduce the time spent connecting to the MySQL server by reusing a previous connection, leaving them open instead of closing when you are done with them.

This improves the latency of queries as you avoid all of the overhead that comes with establishing a new connection.

To explore more Connection Pools examples, please visit the example section createPool.

import mysql from 'mysql2/promise';

// Create the connection pool. The pool-specific settings are the defaults
const pool = mysql.createPool({
  host: 'localhost',
  user: 'root',
  database: 'test',
  waitForConnections: true,
  connectionLimit: 10,
  maxIdle: 10, // max idle connections, the default value is the same as `connectionLimit`
  idleTimeout: 60000, // idle connections timeout, in milliseconds, the default value 60000
  queueLimit: 0,
  enableKeepAlive: true,
  keepAliveInitialDelay: 0,
});
note

The pool does not create all connections upfront but creates them on demand until the connection limit is reached.

You can use the pool in the same way as connections (using pool.query() and pool.execute()):

try {
  // For pool initialization, see above
  const [rows, fields] = await pool.query('SELECT `field` FROM `table`');
  // Connection is automatically released when query resolves
} catch (err) {
  console.log(err);
}

Alternatively, there is also the possibility of manually acquiring a connection from the pool and returning it later:

// For pool initialization, see above
const conn = await pool.getConnection();

// Do something with the connection
await conn.query(/* ... */);

// Don't forget to release the connection when finished!
pool.releaseConnection(conn);
  • Additionally, directly release the connection using the connection object:
conn.release();

Using Promise Wrapperโ€‹

MySQL2 also support Promise API. Which works very well with ES7 async await.

import mysql from 'mysql2/promise';

async function main() {
  // create the connection
  const connection = await mysql.createConnection({
    host: 'localhost',
    user: 'root',
    database: 'test',
  });

  // query database
  const [rows, fields] = await connection.execute(
    'SELECT * FROM `table` WHERE `name` = ? AND `age` > ?',
    ['Morty', 14]
  );
}

MySQL2 use default Promise object available in scope. But you can choose which Promise implementation you want to use.

// get the client
import mysql from 'mysql2/promise';

// get the promise implementation, we will use bluebird
import bluebird from 'bluebird';

// create the connection, specify bluebird as Promise
const connection = await mysql.createConnection({
  host: 'localhost',
  user: 'root',
  database: 'test',
  Promise: bluebird,
});

// query database
const [rows, fields] = await connection.execute(
  'SELECT * FROM `table` WHERE `name` = ? AND `age` > ?',
  ['Morty', 14]
);

MySQL2 also exposes a .promise() function on Pools, so you can create a promise/non-promise connections from the same pool.

import mysql from 'mysql2';

async function main() {
  // create the pool
  const pool = mysql.createPool({
    host: 'localhost',
    user: 'root',
    database: 'test',
  });

  // now get a Promise wrapped instance of that pool
  const promisePool = pool.promise();

  // query database using promises
  const [rows, fields] = await promisePool.query('SELECT 1');
}

MySQL2 exposes a .promise() function on Connections, to "upgrade" an existing non-promise connection to use promise.

const mysql = require('mysql2');

// create the connection
const conn = mysql.createConnection({
  host: 'localhost',
  user: 'root',
  database: 'test',
});

conn
  .promise()
  .query('SELECT 1')
  .then(([rows, fields]) => {
    console.log(rows);
  })
  .catch(console.log)
  .then(() => conn.end());

Array Resultsโ€‹

If you have two columns with the same name, you might want to get results as an array rather than an object to prevent them from clashing. This is a deviation from the Node MySQL library.

For example: SELECT 1 AS `foo`, 2 AS `foo`.

You can enable this setting at either the connection level (applies to all queries), or at the query level (applies only to that specific query).

Connection Levelโ€‹

const conn = await mysql.createConnection({
  host: 'localhost',
  database: 'test',
  user: 'root',
  rowsAsArray: true,
});

Query Levelโ€‹

try {
  const [results, fields] = await conn.query({
    sql: 'SELECT 1 AS `foo`, 2 AS `foo`',
    rowsAsArray: true,
  });

  console.log(results); // in this query, results will be an array of arrays rather than an array of objects
  console.log(fields); // fields are unchanged
} catch (err) {
  console.log(err);
}
Getting Help

Need help? Ask your question on Stack Overflow or GitHub. If you've encountered an issue, please file it on GitHub.