HackFlowy/node_modules/mysql/Readme.md

# node-mysql

[![Build Status](https://secure.travis-ci.org/felixge/node-mysql.png)](http://travis-ci.org/felixge/node-mysql)

## Install

```bash
npm install mysql@2.0.0-alpha7
```

Despite the alpha tag, this is the recommended version for new applications.
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 git://github.com/felixge/node-mysql.git
```

[v0.9 branch]: https://github.com/felixge/node-mysql/tree/v0.9

## 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:

```js
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][].

[GitHub Contributors page]: https://github.com/felixge/node-mysql/graphs/contributors

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.

[Ulf Wendel]: http://blog.ulf-wendel.de/
[Andrey Hristov]: http://andrey.hristov.com/

## Sponsors

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

* [Transloadit](http://transloadit.com) (my startup, we do file uploading &
  video encoding as a service, check it out)
* [Joyent](http://www.joyent.com/)
* [pinkbike.com](http://pinkbike.com/)
* [Holiday Extras](http://www.holidayextras.co.uk/) (they are [hiring](http://join.holidayextras.co.uk/vacancy/senior-web-technologist/))
* [Newscope](http://newscope.com/) (they are [hiring](http://www.newscope.com/stellenangebote))

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

[get in touch]: http://felixge.de/consulting

## 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:

```js
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:

```js
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](#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`)
* `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'`)
* `timezone`: The timezone used to store local dates. (Default: `'local'`)
* `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](#custom-format).
* `supportBigNumbers`: When dealing with big numbers in the database, you should enable this option.
* `debug`: Prints protocol details to stdout. (Default: `false`)
* `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](#connection-flags).

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

```js
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:

```js
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.

```js
connection.destroy();
```

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

## Pooling connections

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

```js
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)
});
```

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

```js
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.end();

    // 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:

* `createConnection`: The function to use to create the connection. (Default:
  `mysql.createConnection`)
* `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`)

## 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:

```js
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, or the server crashing. All of these events are
considered fatal errors, and will have the `err.code =
'PROTOCOL_CONNECTION_LOST'`.  See the [Error Handling](#error-handling) section
for more information.

The best way to handle such unexpected disconnects is shown below:

```js
function handleDisconnect(connection) {
  connection.on('error', function(err) {
    if (!err.fatal) {
      return;
    }

    if (err.code !== 'PROTOCOL_CONNECTION_LOST') {
      throw err;
    }

    console.log('Re-connecting lost connection: ' + err.stack);

    connection = mysql.createConnection(connection.config);
    handleDisconnect(connection);
    connection.connect();
  });
}

handleDisconnect(connection);
```

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()` method:

```js
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:

```js
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:

```js
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:

```js
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:

```js
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.

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

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

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

### 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:

```js
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:

```js
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:

```js
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.

## 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:

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

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

```js
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:

```js
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:

```js
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.

```js
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: '...'
  }, ...]
  */
});
```

## 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.

[Error]: https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Error
[MySQL server error]: http://dev.mysql.com/doc/refman/5.5/en/error-messages-server.html

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:

```js
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:

```js
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:

```js
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:

```js
// 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:

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

Or on the query level:

```js
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:

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

If you need a buffer there's also a `.buffer()` function and also a `.geometry()` one
both used by the default type cast that you can use.

## 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.

```js
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:

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

This will print all incoming and outgoing packets on stdout.

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.

## Todo

* Prepared statements
* setTimeout() for Connection / Query
* Support for encodings other than UTF-8 / ASCII
* API support for transactions, similar to [php](http://www.php.net/manual/en/mysqli.quickstart.transactions.php)