mysql

What is mysql?

The mysql npm package is a Node.js client for interacting with MySQL databases. It allows users to connect to a MySQL database, execute queries, and handle database operations asynchronously.

What are mysql's main functionalities?

Connecting to a MySQL database

This code establishes a connection to a MySQL database using the provided credentials.

const mysql = require('mysql');
const connection = mysql.createConnection({
  host     : 'localhost',
  user     : 'me',
  password : 'secret',
  database : 'my_db'
});
connection.connect();

Executing a query

This code executes a SQL query to select all records from 'my_table' and logs the results.

connection.query('SELECT * FROM my_table', (error, results, fields) => {
  if (error) throw error;
  console.log(results);
});

Inserting data

This code inserts a new record into the 'posts' table with the provided data object.

const post  = {id: 1, title: 'Hello MySQL'};
const query = connection.query('INSERT INTO posts SET ?', post, (error, results, fields) => {
  if (error) throw error;
  // Neat!
});

Updating data

This code updates the title of a record in the 'posts' table where the id is 5.

connection.query('UPDATE posts SET title = ? WHERE id = ?', ['Hello World', 5], (error, results, fields) => {
  if (error) throw error;
  // Updated successfully
});

Closing the connection

This code closes the connection to the MySQL database.

connection.end();

Other packages similar to mysql

pg

The pg package is a PostgreSQL client for Node.js. Similar to mysql, it allows for connecting to a PostgreSQL database, executing queries, and handling database operations. It is designed specifically for PostgreSQL, whereas mysql is for MySQL databases.

sequelize

Sequelize is a promise-based Node.js ORM for Postgres, MySQL, MariaDB, SQLite, and Microsoft SQL Server. It provides a higher-level abstraction for database interactions and supports transactions, relations, eager and lazy loading, read replication, and more. It is more feature-rich and complex compared to the mysql package, which is a simple query client.

typeorm

TypeORM is an ORM that can run in Node.js and be used with TypeScript or JavaScript (ES5, ES6, ES7, ES8). It supports MySQL, PostgreSQL, MariaDB, SQLite, MS SQL Server, Oracle, WebSQL databases. It provides a lot of advanced features like automatic migrations, data mapping, and a powerful query builder. It is more advanced and feature-rich compared to the mysql package.

knex

Knex.js is a SQL query builder for Postgres, MSSQL, MySQL, MariaDB, SQLite3, Oracle, and Amazon Redshift, designed to be flexible, portable, and fun to use. It provides transaction support, connection pooling, and can be used as an SQL query builder in both Node.js and the browser. It is more versatile in terms of database support compared to the mysql package.

README

node-mysql

Install

npm install mysql

For information about the previous 0.9.x releases, visit the v0.9 branch.

Sometimes I may also ask you to install the latest version from Github to check if a bugfix is working. In this case, please do:

npm install felixge/node-mysql

Introduction

This is a node.js driver for mysql. It is written in JavaScript, does not require compiling, and is 100% MIT licensed.

Here is an example on how to use it:

var mysql      = require('mysql');
var connection = mysql.createConnection({
  host     : 'localhost',
  user     : 'me',
  password : 'secret'
});

connection.connect();

connection.query('SELECT 1 + 1 AS solution', function(err, rows, fields) {
  if (err) throw err;

  console.log('The solution is: ', rows[0].solution);
});

connection.end();

From this example, you can learn the following:

• Every method you invoke on a connection is queued and executed in sequence.
• Closing the connection is done using end() which makes sure all remaining queries are executed before sending a quit packet to the mysql server.

Contributors

Thanks goes to the people who have contributed code to this module, see the GitHub Contributors page.

Additionally I'd like to thank the following people:

• Andrey Hristov (Oracle) - for helping me with protocol questions.
• Ulf Wendel (Oracle) - for helping me with protocol questions.

Sponsors

The following companies have supported this project financially, allowing me to spend more time on it (ordered by time of contribution):

• Transloadit (my startup, we do file uploading & video encoding as a service, check it out)
• Joyent
• pinkbike.com
• Holiday Extras (they are hiring)
• Newscope (they are hiring)

If you are interested in sponsoring a day or more of my time, please get in touch.

Community

If you'd like to discuss this module, or ask questions about it, please use one of the following:

• Mailing list: https://groups.google.com/forum/#!forum/node-mysql
• IRC Channel: #node.js (on freenode.net, I pay attention to any message including the term mysql)

Establishing connections

The recommended way to establish a connection is this:

var mysql      = require('mysql');
var connection = mysql.createConnection({
  host     : 'example.org',
  user     : 'bob',
  password : 'secret'
});

connection.connect(function(err) {
  // connected! (unless `err` is set)
});

However, a connection can also be implicitly established by invoking a query:

var mysql      = require('mysql');
var connection = mysql.createConnection(...);

connection.query('SELECT 1', function(err, rows) {
  // connected! (unless `err` is set)
});

Depending on how you like to handle your errors, either method may be appropriate. Any type of connection error (handshake or network) is considered a fatal error, see the Error Handling section for more information.

Connection options

When establishing a connection, you can set the following options:

• host: The hostname of the database you are connecting to. (Default: localhost)
• port: The port number to connect to. (Default: 3306)
• localAddress: The source IP address to use for TCP connection. (Optional)
• socketPath: The path to a unix domain socket to connect to. When used host and port are ignored.
• user: The MySQL user to authenticate as.
• password: The password of that MySQL user.
• database: Name of the database to use for this connection (Optional).
• charset: The charset for the connection. (Default: 'UTF8_GENERAL_CI'. Value needs to be all in upper case letters!)
• timezone: The timezone used to store local dates. (Default: 'local')
• connectTimeout: The milliseconds before a timeout occurs during the initial connection to the MySQL server. (Default: no timeout)
• stringifyObjects: Stringify objects instead of converting to values. See issue #501. (Default: 'false')
• insecureAuth: Allow connecting to MySQL instances that ask for the old (insecure) authentication method. (Default: false)
• typeCast: Determines if column values should be converted to native JavaScript types. (Default: true)
• queryFormat: A custom query format function. See Custom format.
• supportBigNumbers: When dealing with big numbers (BIGINT and DECIMAL columns) in the database, you should enable this option (Default: false).
• bigNumberStrings: Enabling both supportBigNumbers and bigNumberStrings forces big numbers (BIGINT and DECIMAL columns) to be always returned as JavaScript String objects (Default: false). Enabling supportBigNumbers but leaving bigNumberStrings disabled will return big numbers as String objects only when they cannot be accurately represented with [JavaScript Number objects] (http://ecma262-5.com/ELS5_HTML.htm#Section_8.5) (which happens when they exceed the [-2^53, +2^53] range), otherwise they will be returned as Number objects. This option is ignored if supportBigNumbers is disabled.
• dateStrings: Force date types (TIMESTAMP, DATETIME, DATE) to be returned as strings rather then inflated into JavaScript Date objects. (Default: false)
• debug: Prints protocol details to stdout. (Default: false)
• trace: Generates stack traces on Error to include call site of library entrance ("long stack traces"). Slight performance penalty for most calls. (Default: true)
• multipleStatements: Allow multiple mysql statements per query. Be careful with this, it exposes you to SQL injection attacks. (Default: false)
• flags: List of connection flags to use other than the default ones. It is also possible to blacklist default ones. For more information, check Connection Flags.
• ssl: object with ssl parameters ( same format as crypto.createCredentials argument ) or a string containing name of ssl profile. Currently only 'Amazon RDS' profile is bundled, containing CA from https://rds.amazonaws.com/doc/rds-ssl-ca-cert.pem

In addition to passing these options as an object, you can also use a url string. For example:

var connection = mysql.createConnection('mysql://user:pass@host/db?debug=true&charset=BIG5_CHINESE_CI&timezone=-0700');

Note: The query values are first attempted to be parsed as JSON, and if that fails assumed to be plaintext strings.

Terminating connections

There are two ways to end a connection. Terminating a connection gracefully is done by calling the end() method:

connection.end(function(err) {
  // The connection is terminated now
});

This will make sure all previously enqueued queries are still before sending a COM_QUIT packet to the MySQL server. If a fatal error occurs before the COM_QUIT packet can be sent, an err argument will be provided to the callback, but the connection will be terminated regardless of that.

An alternative way to end the connection is to call the destroy() method. This will cause an immediate termination of the underlying socket. Additionally destroy() guarantees that no more events or callbacks will be triggered for the connection.

connection.destroy();

Unlike end() the destroy() method does not take a callback argument.

Pooling connections

Use pool directly.

var mysql = require('mysql');
var pool  = mysql.createPool({
  host     : 'example.org',
  user     : 'bob',
  password : 'secret'
});

pool.query('SELECT 1 + 1 AS solution', function(err, rows, fields) {
  if (err) throw err;

  console.log('The solution is: ', rows[0].solution);
});

Connections can be pooled to ease sharing a single connection, or managing multiple connections.

var mysql = require('mysql');
var pool  = mysql.createPool({
  host     : 'example.org',
  user     : 'bob',
  password : 'secret'
});

pool.getConnection(function(err, connection) {
  // connected! (unless `err` is set)
});

If you need to set session variables on the connection before it gets used, you can listen to the connection event.

pool.on('connection', function(connection) {
  connection.query('SET SESSION auto_increment_increment=1')
});

When you are done with a connection, just call connection.release() and the connection will return to the pool, ready to be used again by someone else.

var mysql = require('mysql');
var pool  = mysql.createPool(...);

pool.getConnection(function(err, connection) {
  // Use the connection
  connection.query( 'SELECT something FROM sometable', function(err, rows) {
    // And done with the connection.
    connection.release();

    // Don't use the connection here, it has been returned to the pool.
  });
});

If you would like to close the connection and remove it from the pool, use connection.destroy() instead. The pool will create a new connection the next time one is needed.

Connections are lazily created by the pool. If you configure the pool to allow up to 100 connections, but only ever use 5 simultaneously, only 5 connections will be made. Connections are also cycled round-robin style, with connections being taken from the top of the pool and returning to the bottom.

Pool options

Pools accept all the same options as a connection. When creating a new connection, the options are simply passed to the connection constructor. In addition to those options pools accept a few extras:

• waitForConnections: Determines the pool's action when no connections are available and the limit has been reached. If true, the pool will queue the connection request and call it when one becomes available. If false, the pool will immediately call back with an error. (Default: true)
• connectionLimit: The maximum number of connections to create at once. (Default: 10)
• queueLimit: The maximum number of connection requests the pool will queue before returning an error from getConnection. If set to 0, there is no limit to the number of queued connection requests. (Default: 0)

PoolCluster

PoolCluster provides multiple hosts connection. (group & retry & selector)

// create
var poolCluster = mysql.createPoolCluster();

poolCluster.add(config); // anonymous group
poolCluster.add('MASTER', masterConfig);
poolCluster.add('SLAVE1', slave1Config);
poolCluster.add('SLAVE2', slave2Config);

// Target Group : ALL(anonymous, MASTER, SLAVE1-2), Selector : round-robin(default)
poolCluster.getConnection(function (err, connection) {});

// Target Group : MASTER, Selector : round-robin
poolCluster.getConnection('MASTER', function (err, connection) {});

// Target Group : SLAVE1-2, Selector : order
// If can't connect to SLAVE1, return SLAVE2. (remove SLAVE1 in the cluster)
poolCluster.on('remove', function (nodeId) {
  console.log('REMOVED NODE : ' + nodeId); // nodeId = SLAVE1 
});

poolCluster.getConnection('SLAVE*', 'ORDER', function (err, connection) {});

// of namespace : of(pattern, selector)
poolCluster.of('*').getConnection(function (err, connection) {});

var pool = poolCluster.of('SLAVE*', 'RANDOM');
pool.getConnection(function (err, connection) {});
pool.getConnection(function (err, connection) {});

// destroy
poolCluster.end();

PoolCluster Option

• canRetry: If true, PoolCluster will attempt to reconnect when connection fails. (Default: true)
• removeNodeErrorCount: If connection fails, node's errorCount increases. When errorCount is greater than removeNodeErrorCount, remove a node in the PoolCluster. (Default: 5)
• defaultSelector: The default selector. (Default: RR)
  • RR: Select one alternately. (Round-Robin)
  • RANDOM: Select the node by random function.
  • ORDER: Select the first node available unconditionally.

var clusterConfig = {
  removeNodeErrorCount: 1, // Remove the node immediately when connection fails.
  defaultSelector: 'ORDER'
};

var poolCluster = mysql.createPoolCluster(clusterConfig);

Switching users / altering connection state

MySQL offers a changeUser command that allows you to alter the current user and other aspects of the connection without shutting down the underlying socket:

connection.changeUser({user : 'john'}, function(err) {
  if (err) throw err;
});

The available options for this feature are:

• user: The name of the new user (defaults to the previous one).
• password: The password of the new user (defaults to the previous one).
• charset: The new charset (defaults to the previous one).
• database: The new database (defaults to the previous one).

A sometimes useful side effect of this functionality is that this function also resets any connection state (variables, transactions, etc.).

Errors encountered during this operation are treated as fatal connection errors by this module.

Server disconnects

You may lose the connection to a MySQL server due to network problems, the server timing you out, the server being restarted, or crashing. All of these events are considered fatal errors, and will have the err.code = 'PROTOCOL_CONNECTION_LOST'. See the Error Handling section for more information.

A good way to handle such unexpected disconnects is shown below:

var db_config = {
  host: 'localhost',
	user: 'root',
	password: '',
	database: 'example'
};

var connection;

function handleDisconnect() {
  connection = mysql.createConnection(db_config); // Recreate the connection, since
                                                  // the old one cannot be reused.

  connection.connect(function(err) {              // The server is either down
    if(err) {                                     // or restarting (takes a while sometimes).
      console.log('error when connecting to db:', err);
      setTimeout(handleDisconnect, 2000); // We introduce a delay before attempting to reconnect,
    }                                     // to avoid a hot loop, and to allow our node script to
  });                                     // process asynchronous requests in the meantime.
                                          // If you're also serving http, display a 503 error.
  connection.on('error', function(err) {
    console.log('db error', err);
    if(err.code === 'PROTOCOL_CONNECTION_LOST') { // Connection to the MySQL server is usually
      handleDisconnect();                         // lost due to either server restart, or a
    } else {                                      // connnection idle timeout (the wait_timeout
      throw err;                                  // server variable configures this)
    }
  });
}

handleDisconnect();

As you can see in the example above, re-connecting a connection is done by establishing a new connection. Once terminated, an existing connection object cannot be re-connected by design.

With Pool, disconnected connections will be removed from the pool freeing up space for a new connection to be created on the next getConnection call.

Escaping query values

In order to avoid SQL Injection attacks, you should always escape any user provided data before using it inside a SQL query. You can do so using the connection.escape() or pool.escape() methods:

var userId = 'some user provided value';
var sql    = 'SELECT * FROM users WHERE id = ' + connection.escape(userId);
connection.query(sql, function(err, results) {
  // ...
});

Alternatively, you can use ? characters as placeholders for values you would like to have escaped like this:

connection.query('SELECT * FROM users WHERE id = ?', [userId], function(err, results) {
  // ...
});

This looks similar to prepared statements in MySQL, however it really just uses the same connection.escape() method internally.

Different value types are escaped differently, here is how:

• Numbers are left untouched
• Booleans are converted to true / false strings
• Date objects are converted to 'YYYY-mm-dd HH:ii:ss' strings
• Buffers are converted to hex strings, e.g. X'0fa5'
• Strings are safely escaped
• Arrays are turned into list, e.g. ['a', 'b'] turns into 'a', 'b'
• Nested arrays are turned into grouped lists (for bulk inserts), e.g. [['a', 'b'], ['c', 'd']] turns into ('a', 'b'), ('c', 'd')
• Objects are turned into key = 'val' pairs. Nested objects are cast to strings.
• undefined / null are converted to NULL
• NaN / Infinity are left as-is. MySQL does not support these, and trying to insert them as values will trigger MySQL errors until they implement support.

If you paid attention, you may have noticed that this escaping allows you to do neat things like this:

var post  = {id: 1, title: 'Hello MySQL'};
var query = connection.query('INSERT INTO posts SET ?', post, function(err, result) {
  // Neat!
});
console.log(query.sql); // INSERT INTO posts SET `id` = 1, `title` = 'Hello MySQL'

If you feel the need to escape queries by yourself, you can also use the escaping function directly:

var query = "SELECT * FROM posts WHERE title=" + mysql.escape("Hello MySQL");

console.log(query); // SELECT * FROM posts WHERE title='Hello MySQL'

Escaping query identifiers

If you can't trust an SQL identifier (database / table / column name) because it is provided by a user, you should escape it with mysql.escapeId(identifier) like this:

var sorter = 'date';
var query = 'SELECT * FROM posts ORDER BY ' + mysql.escapeId(sorter);

console.log(query); // SELECT * FROM posts ORDER BY `date`

It also supports adding qualified identifiers. It will escape both parts.

var sorter = 'date';
var query = 'SELECT * FROM posts ORDER BY ' + mysql.escapeId('posts.' + sorter);

console.log(query); // SELECT * FROM posts ORDER BY `posts`.`date`

Alternatively, you can use ?? characters as placeholders for identifiers you would like to have escaped like this:

var userId = 1;
var columns = ['username', 'email'];
var query = connection.query('SELECT ?? FROM ?? WHERE id = ?', [columns, 'users', userId], function(err, results) {
  // ...
});

console.log(query.sql); // SELECT `username`, `email` FROM `users` WHERE id = 1

Please note that this last character sequence is experimental and syntax might change

When you pass an Object to .escape() or .query(), .escapeId() is used to avoid SQL injection in object keys.

Preparing Queries

You can use mysql.format to prepare a query with multiple insertion points, utilizing the proper escaping for ids and values. A simple example of this follows:

var sql = "SELECT * FROM ?? WHERE ?? = ?";
var inserts = ['users', 'id', userId];
sql = mysql.format(sql, inserts);

Following this you then have a valid, escaped query that you can then send to the database safely. This is useful if you are looking to prepare the query before actually sending it to the database. As mysql.format is exposed from SqlString.format you also have the option (but are not required) to pass in stringifyObject and timezone, allowing you provide a custom means of turning objects into strings, as well as a location-specific/timezone-aware Date.

Custom format

If you prefer to have another type of query escape format, there's a connection configuration option you can use to define a custom format function. You can access the connection object if you want to use the built-in .escape() or any other connection function.

Here's an example of how to implement another format:

connection.config.queryFormat = function (query, values) {
  if (!values) return query;
  return query.replace(/\:(\w+)/g, function (txt, key) {
    if (values.hasOwnProperty(key)) {
      return this.escape(values[key]);
    }
    return txt;
  }.bind(this));
};

connection.query("UPDATE posts SET title = :title", { title: "Hello MySQL" });

Getting the id of an inserted row

If you are inserting a row into a table with an auto increment primary key, you can retrieve the insert id like this:

connection.query('INSERT INTO posts SET ?', {title: 'test'}, function(err, result) {
  if (err) throw err;

  console.log(result.insertId);
});

When dealing with big numbers (above JavaScript Number precision limit), you should consider enabling supportBigNumbers option to be able to read the insert id as a string, otherwise it will throw.

This option is also required when fetching big numbers from the database, otherwise you will get values rounded to hundreds or thousands due to the precision limit.

Executing queries in parallel

The MySQL protocol is sequential, this means that you need multiple connections to execute queries in parallel. You can use a Pool to manage connections, one simple approach is to create one connection per incoming http request.

Streaming query rows

Sometimes you may want to select large quantities of rows and process each of them as they are received. This can be done like this:

var query = connection.query('SELECT * FROM posts');
query
  .on('error', function(err) {
    // Handle error, an 'end' event will be emitted after this as well
  })
  .on('fields', function(fields) {
    // the field packets for the rows to follow
  })
  .on('result', function(row) {
    // Pausing the connnection is useful if your processing involves I/O
    connection.pause();

    processRow(row, function() {
      connection.resume();
    });
  })
  .on('end', function() {
    // all rows have been received
  });

Please note a few things about the example above:

• Usually you will want to receive a certain amount of rows before starting to throttle the connection using pause(). This number will depend on the amount and size of your rows.
• pause() / resume() operate on the underlying socket and parser. You are guaranteed that no more 'result' events will fire after calling pause().
• You MUST NOT provide a callback to the query() method when streaming rows.
• The 'result' event will fire for both rows as well as OK packets confirming the success of a INSERT/UPDATE query.

Additionally you may be interested to know that it is currently not possible to stream individual row columns, they will always be buffered up entirely. If you have a good use case for streaming large fields to and from MySQL, I'd love to get your thoughts and contributions on this.

Piping results with Streams2

The query object provides a convenience method .stream([options]) that wraps query events into a Readable Streams2 object. This stream can easily be piped downstream and provides automatic pause/resume, based on downstream congestion and the optional highWaterMark. The objectMode parameter of the stream is set to true by default.

For example, piping query results into another stream (with a max buffer of 5 objects) is simply:

connection.query('SELECT * FROM posts')
  .stream({highWaterMark: 5})
  .pipe(...);

Multiple statement queries

Support for multiple statements is disabled for security reasons (it allows for SQL injection attacks if values are not properly escaped). To use this feature you have to enable it for your connection:

var connection = mysql.createConnection({multipleStatements: true});

Once enabled, you can execute multiple statement queries like any other query:

connection.query('SELECT 1; SELECT 2', function(err, results) {
  if (err) throw err;

  // `results` is an array with one element for every statement in the query:
  console.log(results[0]); // [{1: 1}]
  console.log(results[1]); // [{2: 2}]
});

Additionally you can also stream the results of multiple statement queries:

var query = connection.query('SELECT 1; SELECT 2');

query
  .on('fields', function(fields, index) {
    // the fields for the result rows that follow
  })
  .on('result', function(row, index) {
    // index refers to the statement this result belongs to (starts at 0)
  });

If one of the statements in your query causes an error, the resulting Error object contains a err.index property which tells you which statement caused it. MySQL will also stop executing any remaining statements when an error occurs.

Please note that the interface for streaming multiple statement queries is experimental and I am looking forward to feedback on it.

Stored procedures

You can call stored procedures from your queries as with any other mysql driver. If the stored procedure produces several result sets, they are exposed to you the same way as the results for multiple statement queries.

Joins with overlapping column names

When executing joins, you are likely to get result sets with overlapping column names.

By default, node-mysql will overwrite colliding column names in the order the columns are received from MySQL, causing some of the received values to be unavailable.

However, you can also specify that you want your columns to be nested below the table name like this:

var options = {sql: '...', nestTables: true};
connection.query(options, function(err, results) {
  /* results will be an array like this now:
  [{
    table1: {
      fieldA: '...',
      fieldB: '...',
    },
    table2: {
      fieldA: '...',
      fieldB: '...',
    },
  }, ...]
  */
});

Or use a string separator to have your results merged.

var options = {sql: '...', nestTables: '_'};
connection.query(options, function(err, results) {
  /* results will be an array like this now:
  [{
    table1_fieldA: '...',
    table1_fieldB: '...',
    table2_fieldA: '...',
    table2_fieldB: '...',
  }, ...]
  */
});

Transactions

Simple transaction support is available at the connection level:

connection.beginTransaction(function(err) {
  if (err) { throw err; }
  connection.query('INSERT INTO posts SET title=?', title, function(err, result) {
    if (err) { 
      connection.rollback(function() {
        throw err;
      });
    }

	var log = 'Post ' + result.insertId + ' added';

	connection.query('INSERT INTO log SET data=?', log, function(err, result) {
	  if (err) { 
        connection.rollback(function() {
          throw err;
        });
      }  
	  connection.commit(function(err) {
	    if (err) { 
          connection.rollback(function() {
            throw err;
          });
        }
	    console.log('success!');
	  });
    });
  });
});

Please note that beginTransaction(), commit() and rollback() are simply convenience functions that execute the START TRANSACTION, COMMIT, and ROLLBACK commands respectively. It is important to understand that many commands in MySQL can cause an implicit commit, as described in the MySQL documentation

Error handling

This module comes with a consistent approach to error handling that you should review carefully in order to write solid applications.

All errors created by this module are instances of the JavaScript Error object. Additionally they come with two properties:

• err.code: Either a MySQL server error (e.g. 'ER_ACCESS_DENIED_ERROR'), a node.js error (e.g. 'ECONNREFUSED') or an internal error (e.g. 'PROTOCOL_CONNECTION_LOST').
• err.fatal: Boolean, indicating if this error is terminal to the connection object.

Fatal errors are propagated to all pending callbacks. In the example below, a fatal error is triggered by trying to connect to an invalid port. Therefore the error object is propagated to both pending callbacks:

var connection = require('mysql').createConnection({
  port: 84943, // WRONG PORT
});

connection.connect(function(err) {
  console.log(err.code); // 'ECONNREFUSED'
  console.log(err.fatal); // true
});

connection.query('SELECT 1', function(err) {
  console.log(err.code); // 'ECONNREFUSED'
  console.log(err.fatal); // true
});

Normal errors however are only delegated to the callback they belong to. So in the example below, only the first callback receives an error, the second query works as expected:

connection.query('USE name_of_db_that_does_not_exist', function(err, rows) {
  console.log(err.code); // 'ER_BAD_DB_ERROR'
});

connection.query('SELECT 1', function(err, rows) {
  console.log(err); // null
  console.log(rows.length); // 1
});

Last but not least: If a fatal errors occurs and there are no pending callbacks, or a normal error occurs which has no callback belonging to it, the error is emitted as an 'error' event on the connection object. This is demonstrated in the example below:

connection.on('error', function(err) {
  console.log(err.code); // 'ER_BAD_DB_ERROR'
});

connection.query('USE name_of_db_that_does_not_exist');

Note: 'error' are special in node. If they occur without an attached listener, a stack trace is printed and your process is killed.

tl;dr: This module does not want you to deal with silent failures. You should always provide callbacks to your method calls. If you want to ignore this advice and suppress unhandled errors, you can do this:

// I am Chuck Norris:
connection.on('error', function() {});

Exception Safety

This module is exception safe. That means you can continue to use it, even if one of your callback functions throws an error which you're catching using 'uncaughtException' or a domain.

Type casting

For your convenience, this driver will cast mysql types into native JavaScript types by default. The following mappings exist:

Number

• TINYINT
• SMALLINT
• INT
• MEDIUMINT
• YEAR
• FLOAT
• DOUBLE

Date

• TIMESTAMP
• DATE
• DATETIME

Buffer

• TINYBLOB
• MEDIUMBLOB
• LONGBLOB
• BLOB
• BINARY
• VARBINARY
• BIT (last byte will be filled with 0 bits as necessary)

String

• CHAR
• VARCHAR
• TINYTEXT
• MEDIUMTEXT
• LONGTEXT
• TEXT
• ENUM
• SET
• DECIMAL (may exceed float precision)
• BIGINT (may exceed float precision)
• TIME (could be mapped to Date, but what date would be set?)
• GEOMETRY (never used those, get in touch if you do)

It is not recommended (and may go away / change in the future) to disable type casting, but you can currently do so on either the connection:

var connection = require('mysql').createConnection({typeCast: false});

Or on the query level:

var options = {sql: '...', typeCast: false};
var query = connection.query(options, function(err, results) {

});

You can also pass a function and handle type casting yourself. You're given some column information like database, table and name and also type and length. If you just want to apply a custom type casting to a specific type you can do it and then fallback to the default. Here's an example of converting TINYINT(1) to boolean:

connection.query({
  sql: '...',
  typeCast: function (field, next) {
    if (field.type == 'TINY' && field.length == 1) {
      return (field.string() == '1'); // 1 = true, 0 = false
    }
    return next();
  }
});

WARNING: YOU MUST INVOKE the parser using one of these three field functions in your custom typeCast callback. They can only be called once.( see #539 for discussion)

field.string()
field.buffer()
field.geometry()

are aliases for

parser.parseLengthCodedString()
parser.parseLengthCodedBuffer()
parser.parseGeometryValue()

You can find which field function you need to use by looking at: RowDataPacket.prototype._typeCast

Connection Flags

If, for any reason, you would like to change the default connection flags, you can use the connection option flags. Pass a string with a comma separated list of items to add to the default flags. If you don't want a default flag to be used prepend the flag with a minus sign. To add a flag that is not in the default list, don't prepend it with a plus sign, just write the flag name (case insensitive).

Please note that some available flags that are not default are still not supported (e.g.: SSL, Compression). Use at your own risk.

Example

The next example blacklists FOUND_ROWS flag from default connection flags.

var connection = mysql.createConnection("mysql://localhost/test?flags=-FOUND_ROWS");

Default Flags

• LONG_PASSWORD
• FOUND_ROWS
• LONG_FLAG
• CONNECT_WITH_DB
• ODBC
• LOCAL_FILES
• IGNORE_SPACE
• PROTOCOL_41
• IGNORE_SIGPIPE
• TRANSACTIONS
• RESERVED
• SECURE_CONNECTION
• MULTI_RESULTS
• MULTI_STATEMENTS (used if multipleStatements option is activated)

Other Available Flags

• NO_SCHEMA
• COMPRESS
• INTERACTIVE
• SSL
• PS_MULTI_RESULTS
• PLUGIN_AUTH
• SSL_VERIFY_SERVER_CERT
• REMEMBER_OPTIONS

Debugging and reporting problems

If you are running into problems, one thing that may help is enabling the debug mode for the connection:

var connection = mysql.createConnection({debug: true});

This will print all incoming and outgoing packets on stdout. You can also restrict debugging to packet types by passing an array of types to debug:

var connection = mysql.createConnection({debug: ['ComQueryPacket', 'RowDataPacket']});

to restrict debugging to the query and data packets.

If that does not help, feel free to open a GitHub issue. A good GitHub issue will have:

• The minimal amount of code required to reproduce the problem (if possible)
• As much debugging output and information about your environment (mysql version, node version, os, etc.) as you can gather.

Running unit tests

Set the environment variables MYSQL_DATABASE, MYSQL_HOST, MYSQL_PORT, MYSQL_USER and MYSQL_PASSWORD. (You may want to put these in a config.sh file and source it when you run the tests). Then run make test.

For example, if you have an installation of mysql running on localhost:3306 and no password set for the root user, run:

  mysql -u root -e "CREATE DATABASE IF NOT EXISTS node_mysql_test"
  MYSQL_HOST=localhost MYSQL_PORT=3306 MYSQL_DATABASE=node_mysql_test MYSQL_USER=root MYSQL_PASSWORD= make test

Running unit tests on windows

• Edit the variables in the file make.bat according to your system and mysql-settings.
• Make sure the database (e.g. 'test') you want to use exists and the user you entered has the proper rights to use the test database. (E.g. do not forget to execute the SQL-command FLUSH PRIVILEGES after you have created the user.)
• In a DOS-box (or CMD-shell) in the folder of your application run npm install mysql --dev or in the mysql folder (node_modules\mysql), run npm install --dev. (This will install additional developer-dependencies for node-mysql.)
• Run npm test mysql in your applications folder or npm test in the mysql subfolder.
• If you want to log the output into a file use npm test mysql > test.log or npm test > test.log.

Todo

• Prepared statements
• setTimeout() for Connection / Query
• Support for encodings other than UTF-8 / ASCII