mssql/README.md

Microsoft SQL Server client for Node.js.

# node-mssql

**Microsoft SQL Server client for Node.js**

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Supported TDS drivers:

- [Tedious][tedious-url] (pure JavaScript - Windows/macOS/Linux, default)
- [MSNodeSQLv8][msnodesqlv8-url] (Microsoft / Contributors Node V8 Driver for Node.js for SQL Server, v2 native - Windows or Linux/macOS 64 bits only)

## Installation

### Tedious driver (default)

```
npm install mssql
```

### MSNodeSQLv8 driver (optional)

```
npm install mssql msnodesqlv8
```

## SQL Server prerequisites

This package requires TCP/IP to connect to SQL Server, and you may need to enable this in your installation.

## Short Example: Use Connect String

```javascript
const sql = require('mssql')

(async () => {
    try {
        // make sure that any items are correctly URL encoded in the connection string
        await sql.connect('Server=localhost,1433;Database=database;User Id=username;Password=password;Encrypt=true')
        const result = await sql.query`select * from mytable where id = ${value}`
        console.dir(result)
    } catch (err) {
        // ... error checks
    }
})()
```

If you're on Windows Azure, add `?encrypt=true` to your connection string. See [docs](#configuration) to learn more.

Parts of the connection URI should be correctly URL encoded so that the URI can be parsed correctly.

## Longer Example: Connect via Config Object

Assuming you have set the appropriate environment variables, you can construct a config object as follows:

```javascript
const sql = require('mssql')

const sqlConfig = {
  user: process.env.DB_USER,
  password: process.env.DB_PWD,
  database: process.env.DB_NAME,
  server: 'localhost',
  pool: {
    max: 10,
    min: 0,
    idleTimeoutMillis: 30000
  },
  options: {
    encrypt: true, // for azure
    trustServerCertificate: false // change to true for local dev / self-signed certs
  }
}

(async () => {
 try {
  // make sure that any items are correctly URL encoded in the connection string
  await sql.connect(sqlConfig)
  const result = await sql.query`select * from mytable where id = ${value}`
  console.dir(result)
 } catch (err) {
  // ... error checks
 }
})()
```

## Windows Authentication Example Using MSNodeSQLv8

```javascript
const sql = require('mssql/msnodesqlv8');

const config = {
  server: "MyServer",
  database: "MyDatabase",
  options: {
    trustedConnection: true, // Set to true if using Windows Authentication
    trustServerCertificate: true, // Set to true if using self-signed certificates
  },
  driver: "msnodesqlv8", // Required if using Windows Authentication
};

(async () => {
  try {
    await sql.connect(config);
    const result = await sql.query`select TOP 10 * from MyTable`;
    console.dir(result);
  } catch (err) {
    console.error(err);
  }
})();
```

## Documentation

### Examples

* [Async/Await](#asyncawait)
* [Promises](#promises)
* [ES6 Tagged template literals](#es6-tagged-template-literals)
* [Callbacks](#callbacks)
* [Streaming](#streaming)
* [Connection Pools](#connection-pools)

### Configuration

* [General](#general-same-for-all-drivers)
* [Formats](#formats)

### Drivers

* [Tedious](#tedious)
* [MSNodeSQLv8](#msnodesqlv8)

### Connections

* [Pool Management](#pool-management)
* [ConnectionPool](#connections-1)
* [connect](#connect-callback)
* [close](#close)

### Requests

* [Request](#request)
* [execute](#execute-procedure-callback)
* [input](#input-name-type-value)
* [output](#output-name-type-value)
* [toReadableStream](#toReadableStream)
* [pipe](#pipe-stream)
* [query](#query-command-callback)
* [batch](#batch-batch-callback)
* [bulk](#bulk-table-options-callback)
* [cancel](#cancel)

### Transactions

* [Transaction](#transaction)
* [begin](#begin-isolationlevel-callback)
* [commit](#commit-callback)
* [rollback](#rollback-callback)

### Prepared Statements

* [PreparedStatement](#prepared-statement)
* [input](#input-name-type)
* [output](#output-name-type)
* [prepare](#prepare-statement-callback)
* [execute](#execute-values-callback)
* [unprepare](#unprepare-callback)

### Other

* [CLI](#cli)
* [Geography and Geometry](#geography-and-geometry)
* [Table-Valued Parameter](#table-valued-parameter-tvp)
* [Response Schema](#response-schema)
* [Affected Rows](#affected-rows)
* [JSON support](#json-support)
* [Handling Duplicate Column Names](#handling-duplicate-column-names)
* [Errors](#errors)
* [Informational messages](#informational-messages)
* [Metadata](#metadata)
* [Data Types](#data-types)
* [SQL injection](#sql-injection)
* [Known Issues](#known-issues)
* [Contributing](https://github.com/tediousjs/node-mssql/wiki/Contributing)
* [8.x to 9.x changes](#8x-to-9x-changes)
* [7.x to 8.x changes](#7x-to-8x-changes)
* [6.x to 7.x changes](#6x-to-7x-changes)
* [5.x to 6.x changes](#5x-to-6x-changes)
* [4.x to 5.x changes](#4x-to-5x-changes)
* [3.x to 4.x changes](#3x-to-4x-changes)
* [3.x Documentation](https://github.com/tediousjs/node-mssql/blob/1893969195045a250f0fdeeb2de7f30dcf6689ad/README.md)

## Examples

### Config

```javascript
const config = {
    user: '...',
    password: '...',
    server: 'localhost', // You can use 'localhost\\instance' to connect to named instance
    database: '...',
}
```


### Async/Await

```javascript
const sql = require('mssql')

(async function () {
    try {
        let pool = await sql.connect(config)
        let result1 = await pool.request()
            .input('input_parameter', sql.Int, value)
            .query('select * from mytable where id = @input_parameter')

        console.dir(result1)

        // Stored procedure

        let result2 = await pool.request()
            .input('input_parameter', sql.Int, value)
            .output('output_parameter', sql.VarChar(50))
            .execute('procedure_name')

        console.dir(result2)
    } catch (err) {
        // ... error checks
    }
})()

sql.on('error', err => {
    // ... error handler
})
```

### Promises

#### Queries

```javascript
const sql = require('mssql')

sql.on('error', err => {
    // ... error handler
})

sql.connect(config).then(pool => {
    // Query

    return pool.request()
        .input('input_parameter', sql.Int, value)
        .query('select * from mytable where id = @input_parameter')
}).then(result => {
    console.dir(result)
}).catch(err => {
  // ... error checks
});
```

#### Stored procedures

```js
const sql = require('mssql')

sql.on('error', err => {
    // ... error handler
})

sql.connect(config).then(pool => {

    // Stored procedure

    return pool.request()
        .input('input_parameter', sql.Int, value)
        .output('output_parameter', sql.VarChar(50))
        .execute('procedure_name')
}).then(result => {
    console.dir(result)
}).catch(err => {
    // ... error checks
})
```

Native Promise is used by default. You can easily change this with `sql.Promise = require('myownpromisepackage')`.

### ES6 Tagged template literals

```javascript
const sql = require('mssql')

sql.connect(config).then(() => {
    return sql.query`select * from mytable where id = ${value}`
}).then(result => {
    console.dir(result)
}).catch(err => {
    // ... error checks
})

sql.on('error', err => {
    // ... error handler
})
```

All values are automatically sanitized against sql injection.
This is because it is rendered as prepared statement, and thus all limitations imposed in MS SQL on parameters apply.
e.g. Column names cannot be passed/set in statements using variables.

### Callbacks

```javascript
const sql = require('mssql')

sql.connect(config, err => {
    // ... error checks

    // Query

    new sql.Request().query('select 1 as number', (err, result) => {
        // ... error checks

        console.dir(result)
    })

    // Stored Procedure

    new sql.Request()
    .input('input_parameter', sql.Int, value)
    .output('output_parameter', sql.VarChar(50))
    .execute('procedure_name', (err, result) => {
        // ... error checks

        console.dir(result)
    })

    // Using template literal

    const request = new sql.Request()
    request.query(request.template`select * from mytable where id = ${value}`, (err, result) => {
        // ... error checks
        console.dir(result)
    })
})

sql.on('error', err => {
    // ... error handler
})
```

### Streaming

If you plan to work with large amount of rows, you should always use streaming. Once you enable this, you must listen for events to receive data. Events must be attached before the query completes, but can be attached while in-flight.

```javascript
const sql = require('mssql')

sql.connect(config, err => {
    // ... error checks

    const request = new sql.Request()
    request.stream = true // You can set streaming differently for each request

    request.on('recordset', columns => {
        // Emitted once for each recordset in a query
    })

    request.on('row', row => {
        // Emitted for each row in a recordset
    })

    request.on('rowsaffected', rowCount => {
        // Emitted for each `INSERT`, `UPDATE` or `DELETE` statement
        // Requires NOCOUNT to be OFF (default)
    })

    request.on('error', err => {
        // May be emitted multiple times
    })

    request.on('done', result => {
        // Always emitted as the last one
    })
    
    request.query('select * from verylargetable') // or request.execute(procedure)
})

sql.on('error', err => {
    // ... error handler
})
```

When streaming large sets of data you want to back-off or chunk the amount of data you're processing
 to prevent memory exhaustion issues; you can use the `Request.pause()` function to do this. Here is
 an example of managing rows in batches of 15:

```javascript
let rowsToProcess = [];
request.on('row', row => {
  rowsToProcess.push(row);
  if (rowsToProcess.length >= 15) {
    request.pause();
    processRows();
  }
});
request.on('done', () => {
    processRows();
});

function processRows() {
  // process rows
  rowsToProcess = [];
  request.resume();
}
```

## Connection Pools

An important concept to understand when using this library is [Connection Pooling](https://en.wikipedia.org/wiki/Connection_pool) as this library uses connection pooling extensively. As one Node JS process is able to handle multiple requests at once, we can take advantage of this long running process to create a pool of database connections for reuse; this saves overhead of connecting to the database for each request
(as would be the case in something like PHP, where one process handles one request).

With the advantages of pooling comes some added complexities, but these are mostly just conceptual and once you understand how the pooling is working, it is simple to make use of it efficiently and effectively.

### The Global Connection Pool

To assist with pool management in your application there is the `sql.connect()` function that is used to connect to the global connection pool. You can make repeated calls to this function, and if the global pool is already connected, it will resolve to the connected pool. The following example obtains the global connection pool by running `sql.connect()`, and then runs the query against the pool.

NB: It's important to note that there can only be one global connection pool connected at a time. Providing a different connection config to the `connect()` function will not create a new connection if it is already connected.

```js
const sql = require('mssql')
const config = { ... }

// run a query against the global connection pool
function runQuery(query) {
  // sql.connect() will return the existing global pool if it exists or create a new one if it doesn't
  return sql.connect(config).then((pool) => {
    return pool.query(query)
  })
}
```

Awaiting or `.then`-ing the pool creation is a safe way to ensure that the pool is always ready, without knowing where it is needed first. In practice, once the pool is created then there will be no delay for the next `connect()` call.

Also notice that we do *not* close the global pool by calling `sql.close()` after the query is executed, because other queries may need to be run against this pool and closing it will add additional overhead to running subsequent queries. You should only ever close the global pool if you're certain the application is finished. Or for example, if you are running some kind of CLI tool or a CRON job you can close the pool at the end of the script.

### Global Pool Single Instance

The ability to call `connect()` and `close()` repeatedly on the global pool is intended to make pool management easier, however it is better to maintain your own reference to the pool, where `connect()` is called **once**, and the resulting global pool's connection promise is re-used throughout the entire application.

For example, in Express applications, the following approach uses a single global pool instance added to the `app.locals` so the application has access to it when needed. The server start is then chained inside the `connect()` promise.

```js
const express = require('express')
const sql = require('mssql')
const config  = {/*...*/}
//instantiate a connection pool
const appPool = new sql.ConnectionPool(config)
//require route handlers and use the same connection pool everywhere
const route1 = require('./routes/route1')
const app = express()
app.get('/path', route1)

//connect the pool and start the web server when done
appPool.connect().then(function(pool) {
  app.locals.db = pool;
  const server = app.listen(3000, function () {
    const host = server.address().address
    const port = server.address().port
    console.log('Example app listening at http://%s:%s', host, port)
  })
}).catch(function(err) {
  console.error('Error creating connection pool', err)
});
```

Then the route uses the connection pool in the `app.locals` object:

```js
// ./routes/route1.js
const sql = require('mssql');

module.exports = function(req, res) {
  req.app.locals.db.query('SELECT TOP 10 * FROM table_name', function(err, recordset) {
    if (err) {
      console.error(err)
      res.status(500).send('SERVER ERROR')
      return
    }
    res.status(200).json({ message: 'success' })
  })
}
```

### Advanced Pool Management

For some use-cases you may want to implement your own connection pool management, rather than using the global connection pool. Reasons for doing this include:

* Supporting connections to multiple databases
* Creation of separate pools for read vs read/write operations

The following code is an example of a custom connection pool implementation.

```js
// pool-manager.js
const mssql = require('mssql')
const pools = new Map();

module.exports = {
 /**
  * Get or create a pool. If a pool doesn't exist the config must be provided.
  * If the pool does exist the config is ignored (even if it was different to the one provided
  * when creating the pool)
  *
  * @param {string} name
  * @param {{}} [config]
  * @return {Promise.<mssql.ConnectionPool>}
  */
 get: (name, config) => {
  if (!pools.has(name)) {
   if (!config) {
    throw new Error('Pool does not exist');
   }
   const pool = new mssql.ConnectionPool(config);
   // automatically remove the pool from the cache if `pool.close()` is called
   const close = pool.close.bind(pool);
   pool.close = (...args) => {
    pools.delete(name);
    return close(...args);
   }
   pools.set(name, pool.connect());
  }
  return pools.get(name);
 },
 /**
  * Closes all the pools and removes them from the store
  *
  * @return {Promise<mssql.ConnectionPool[]>}
  */
 closeAll: () => Promise.all(Array.from(pools.values()).map((connect) => {
  return connect.then((pool) => pool.close());
 })),
};
```

This file can then be used in your application to create, fetch, and close pools.

```js
const { get } = require('./pool-manager')

async function example() {
  const pool = await get('default')
  return pool.request().query('SELECT 1')
}
```

Similar to the global connection pool, you should aim to only close a pool when you know it will never be needed by the application again. Typically this will only be when your application is shutting down.

### Result value manipulation

In some instances it is desirable to manipulate the record data as it is returned from the database, this may be to cast it as a particular object (eg: `moment` object instead of `Date`) or similar.

In v8.0.0+ it is possible to register per-datatype handlers:

```js
const sql = require('mssql')

// in this example all integer values will return 1 more than their actual value in the database
sql.valueHandler.set(sql.TYPES.Int, (value) => value + 1)

sql.query('SELECT * FROM [example]').then((result) => {
  // all `int` columns will return a manipulated value as per the callback above
})
```

## Configuration

The following is an example configuration object:

```javascript
const config = {
    user: '...',
    password: '...',
    server: 'localhost',
    database: '...',
    pool: {
        max: 10,
        min: 0,
        idleTimeoutMillis: 30000
    }
}
```

### General (same for all drivers)

- **user** - User name to use for authentication.
- **password** - Password to use for authentication.
- **server** - Server to connect to. You can use 'localhost\\instance' to connect to named instance.
- **port** - Port to connect to (default: `1433`). Don't set when connecting to named instance.
- **domain** - Once you set domain, driver will connect to SQL Server using domain login.
- **database** - Database to connect to (default: dependent on server configuration).
- **connectionTimeout** - Connection timeout in ms (default: `15000`).
- **requestTimeout** - Request timeout in ms (default: `15000`). NOTE: msnodesqlv8 driver doesn't support timeouts < 1 second. When passed via connection string, the key must be `request timeout`
- **stream** - Stream recordsets/rows instead of returning them all at once as an argument of callback (default: `false`). You can also enable streaming for each request independently (`request.stream = true`). Always set to `true` if you plan to work with large amount of rows.
- **parseJSON** - Parse JSON recordsets to JS objects (default: `false`). For more information please see section [JSON support](#json-support).
- **pool.max** - The maximum number of connections there can be in the pool (default: `10`).
- **pool.min** - The minimum of connections there can be in the pool (default: `0`).
- **pool.idleTimeoutMillis** - The Number of milliseconds before closing an unused connection (default: `30000`).
- **arrayRowMode** - Return row results as a an array instead of a keyed object. Also adds `columns` array. (default: `false`) See [Handling Duplicate Column Names](#handling-duplicate-column-names)

Complete list of pool options can be found [here](https://github.com/vincit/tarn.js/#usage).

### Formats

In addition to configuration object there is an option to pass config as a connection string. Connection strings are supported.

##### Classic Connection String

###### Standard configuration using tedious driver

```
Server=localhost,1433;Database=database;User Id=username;Password=password;Encrypt=true
```
###### Standard configuration using MSNodeSQLv8 driver
```
Driver=msnodesqlv8;Server=(local)\INSTANCE;Database=database;UID=DOMAIN\username;PWD=password;Encrypt=true
```

##### Azure Active Directory Authentication Connection String

Several types of Azure Authentication are supported:

###### Authentication using Active Directory Integrated
```
Server=*.database.windows.net;Database=database;Authentication=Active Directory Integrated;Client secret=clientsecret;Client Id=clientid;Tenant Id=tenantid;Encrypt=true
```
Note: Internally, the 'Active Directory Integrated' will change its type depending on the other parameters you add to it. On the example above, it will change to azure-active-directory-service-principal-secret because we supplied a Client Id, Client secret and Tenant Id.

If you want to utilize Authentication tokens (azure-active-directory-access-token) Just remove the unnecessary additional parameters and supply only a token parameter, such as in this example:

```
Server=*.database.windows.net;Database=database;Authentication=Active Directory Integrated;token=token;Encrypt=true
```

Finally if you want to utilize managed identity services such as managed identity service app service you can follow this example below:
```
Server=*.database.windows.net;Database=database;Authentication=Active Directory Integrated;msi endpoint=msiendpoint;Client Id=clientid;msi secret=msisecret;Encrypt=true
```
or if its managed identity service virtual machines, then follow this:
```
Server=*.database.windows.net;Database=database;Authentication=Active Directory Integrated;msi endpoint=msiendpoint;Client Id=clientid;Encrypt=true
```

We can also utilizes Active Directory Password but unlike the previous examples, it is not part of the Active Directory Integrated Authentication.

###### Authentication using Active Directory Password
```
Server=*.database.windows.net;Database=database;Authentication=Active Directory Password;User Id=username;Password=password;Client Id=clientid;Tenant Id=tenantid;Encrypt=true
```

For more reference, you can consult [here](https://tediousjs.github.io/tedious/api-connection.html#function_newConnection). Under the authentication.type parameter.

## Drivers

### Tedious

Default driver, actively maintained and production ready. Platform independent, runs everywhere Node.js runs. Officially supported by Microsoft.

**Extra options:**

- **beforeConnect(conn)** - Function, which is invoked before opening the connection. The parameter `conn` is the configured tedious `Connection`. It can be used for attaching event handlers like in this example:
```js
require('mssql').connect({...config, beforeConnect: conn => {
  conn.once('connect', err => { err ? console.error(err) : console.log('mssql connected')})
  conn.once('end', err => { err ? console.error(err) : console.log('mssql disconnected')})
}})
```
- **options.instanceName** - The instance name to connect to. The SQL Server Browser service must be running on the database server, and UDP port 1434 on the database server must be reachable.
- **options.useUTC** - A boolean determining whether or not use UTC time for values without time zone offset (default: `true`).
- **options.encrypt** - A boolean determining whether or not the connection will be encrypted (default: `true`).
- **options.tdsVersion** - The version of TDS to use (default: `7_4`, available: `7_1`, `7_2`, `7_3_A`, `7_3_B`, `7_4`).
- **options.appName** - Application name used for SQL server logging.
- **options.abortTransactionOnError** - A boolean determining whether to rollback a transaction automatically if any error is encountered during the given transaction's execution. This sets the value for `XACT_ABORT` during the initial SQL phase of a connection.

**Authentication:**

On top of the extra options, an `authentication` property can be added to the pool config option

- **authentication** - An object with authentication settings, according to the [Tedious Documentation](https://tediousjs.github.io/tedious/api-connection.html). Passing this object will override `user`, `password`, `domain` settings.
- **authentication.type** - Type of the authentication method, valid types are `default`, `ntlm`, `azure-active-directory-password`, `azure-active-directory-access-token`, `azure-active-directory-msi-vm`, or `azure-active-directory-msi-app-service`
- **authentication.options** - Options of the authentication required by the `tedious` driver, depends on `authentication.type`. For more details, check [Tedious Authentication Interfaces](https://github.com/tediousjs/tedious/blob/v11.1.1/src/connection.ts#L200-L318)
- `tedious` does not support Windows Authentication/Trusted Connection, however the `msnodesqlv8` driver does.

More information about Tedious specific options: http://tediousjs.github.io/tedious/api-connection.html

___

### MSNodeSQLv8

Alternative driver, requires Node.js v10+ or newer; Windows (32 or 64-bit) or Linux/macOS (64-bit only). It's not part of the default package so it must be [installed](#msnodesqlv8-driver) in addition. Supports [Windows/Trusted Connection authentication](#windows-authentication-example-using-msnodesqlv8).

**To use this driver you must use this `require` statement:**

```javascript
const sql = require('mssql/msnodesqlv8')
```

Note: If you use import into your lib to prepare your request (`const { VarChar } = require('mssql')`) you also need to upgrade all your types import into your code (`const { VarChar } = require('mssql/msnodesqlv8')`) or a `connection.on is not a function` error will be thrown.


**Extra options:**

- **beforeConnect(conn)** - Function, which is invoked before opening the connection. The parameter `conn` is the connection configuration, that can be modified to pass extra parameters to the driver's `open()` method.
- **connectionString** - Connection string (default: see below).
- **options.instanceName** - The instance name to connect to. The SQL Server Browser service must be running on the database server, and UDP port 1444 on the database server must be reachable.
- **options.trustedConnection** - Use Windows Authentication (default: `false`).
- **options.useUTC** - A boolean determining whether or not to use UTC time for values without time zone offset (default: `true`).

Default connection string when connecting to port:
```
Driver={SQL Server Native Client 11.0};Server={#{server},#{port}};Database={#{database}};Uid={#{user}};Pwd={#{password}};Trusted_Connection={#{trusted}};
```

Default connection string when connecting to named instance:
```
Driver={SQL Server Native Client 11.0};Server={#{server}\\#{instance}};Database={#{database}};Uid={#{user}};Pwd={#{password}};Trusted_Connection={#{trusted}};
```

Please note that the connection string with this driver is not the same than tedious and use yes/no instead of true/false. You can see more on the [ODBC](https://docs.microsoft.com/fr-fr/dotnet/api/system.data.odbc.odbcconnection.connectionstring?view=dotnet-plat-ext-5.0) documentation.

___

## Connections

Internally, each `ConnectionPool` instance is a separate pool of TDS connections. Once you create a new `Request`/`Transaction`/`Prepared Statement`, a new TDS connection is acquired from the pool and reserved for desired action. Once the action is complete, connection is released back to the pool. Connection health check is built-in so once the dead connection is discovered, it is immediately replaced with a new one.

**IMPORTANT**: Always attach an `error` listener to created connection. Whenever something goes wrong with the connection it will emit an error and if there is no listener it will crash your application with an uncaught error.

```javascript
const pool = new sql.ConnectionPool({ /* config */ })
```

### Events

- **error(err)** - Dispatched on connection error.

---------------------------------------

### connect ([callback])

Create a new connection pool. The initial probe connection is created to find out whether the configuration is valid.

__Arguments__

- **callback(err)** - A callback which is called after initial probe connection has established, or an error has occurred. Optional. If omitted, returns [Promise](#promises).

__Example__

```javascript
const pool = new sql.ConnectionPool({
    user: '...',
    password: '...',
    server: 'localhost',
    database: '...'
})

pool.connect(err => {
    // ...
})
```

__Errors__
- ELOGIN (`ConnectionError`) - Login failed.
- ETIMEOUT (`ConnectionError`) - Connection timeout.
- EALREADYCONNECTED (`ConnectionError`) - Database is already connected!
- EALREADYCONNECTING (`ConnectionError`) - Already connecting to database!
- EINSTLOOKUP (`ConnectionError`) - Instance lookup failed.
- ESOCKET (`ConnectionError`) - Socket error.

---------------------------------------

### close()

Close all active connections in the pool.

__Example__

```javascript
pool.close()
```

## Request

```javascript
const request = new sql.Request(/* [pool or transaction] */)
```

If you omit pool/transaction argument, global pool is used instead.

### Events

- **recordset(columns)** - Dispatched when metadata for new recordset are parsed.
- **row(row)** - Dispatched when new row is parsed.
- **done(returnValue)** - Dispatched when request is complete.
- **error(err)** - Dispatched on error.
- **info(message)** - Dispatched on informational message.

---------------------------------------

### execute (procedure, [callback])

Call a stored procedure.

__Arguments__

- **procedure** - Name of the stored procedure to be executed.
- **callback(err, recordsets, returnValue)** - A callback which is called after execution has completed, or an error has occurred. `returnValue` is also accessible as property of recordsets. Optional. If omitted, returns [Promise](#promises).

__Example__

```javascript
const request = new sql.Request()
request.input('input_parameter', sql.Int, value)
request.output('output_parameter', sql.Int)
request.execute('procedure_name', (err, result) => {
    // ... error checks

    console.log(result.recordsets.length) // count of recordsets returned by the procedure
    console.log(result.recordsets[0].length) // count of rows contained in first recordset
    console.log(result.recordset) // first recordset from result.recordsets
    console.log(result.returnValue) // procedure return value
    console.log(result.output) // key/value collection of output values
    console.log(result.rowsAffected) // array of numbers, each number represents the number of rows affected by executed statemens

    // ...
})
```

__Errors__
- EREQUEST (`RequestError`) - *Message from SQL Server*
- ECANCEL (`RequestError`) - Cancelled.
- ETIMEOUT (`RequestError`) - Request timeout.
- ENOCONN (`RequestError`) - No connection is specified for that request.
- ENOTOPEN (`ConnectionError`) - Connection not yet open.
- ECONNCLOSED (`ConnectionError`) - Connection is closed.
- ENOTBEGUN (`TransactionError`) - Transaction has not begun.
- EABORT (`TransactionError`) - Transaction was aborted (by user or because of an error).

---------------------------------------

### input (name, [type], value)

Add an input parameter to the request.

__Arguments__

- **name** - Name of the input parameter without @ char.
- **type** - SQL data type of input parameter. If you omit type, module automatically decide which SQL data type should be used based on JS data type.
- **value** - Input parameter value. `undefined` and `NaN` values are automatically converted to `null` values.

__Example__

```javascript
request.input('input_parameter', value)
request.input('input_parameter', sql.Int, value)
```

__JS Data Type To SQL Data Type Map__

- `String` -> `sql.NVarChar`
- `Number` -> `sql.Int`
- `Boolean` -> `sql.Bit`
- `Date` -> `sql.DateTime`
- `Buffer` -> `sql.VarBinary`
- `sql.Table` -> `sql.TVP`

Default data type for unknown object is `sql.NVarChar`.

You can define your own type map.

```javascript
sql.map.register(MyClass, sql.Text)
```

You can also overwrite the default type map.

```javascript
sql.map.register(Number, sql.BigInt)
```

__Errors__ (synchronous)
- EARGS (`RequestError`) - Invalid number of arguments.
- EINJECT (`RequestError`) - SQL injection warning.

---------------------------------------

NB: Do not use parameters `@p{n}` as these are used by the internal drivers and cause a conflict.

### output (name, type, [value])

Add an output parameter to the request.

__Arguments__

- **name** - Name of the output parameter without @ char.
- **type** - SQL data type of output parameter.
- **value** - Output parameter value initial value. `undefined` and `NaN` values are automatically converted to `null` values. Optional.

__Example__

```javascript
request.output('output_parameter', sql.Int)
request.output('output_parameter', sql.VarChar(50), 'abc')
```

__Errors__ (synchronous)
- EARGS (`RequestError`) - Invalid number of arguments.
- EINJECT (`RequestError`) - SQL injection warning.

---------------------------------------

### toReadableStream

Convert request to a Node.js ReadableStream

__Example__

```javascript
const { pipeline } = require('stream')
const request = new sql.Request()
const readableStream = request.toReadableStream()
pipeline(readableStream, transformStream, writableStream)
request.query('select * from mytable')
```

OR if you wanted to increase the highWaterMark of the read stream to buffer more rows in memory

```javascript
const { pipeline } = require('stream')
const request = new sql.Request()
const readableStream = request.toReadableStream({ highWaterMark: 100 })
pipeline(readableStream, transformStream, writableStream)
request.query('select * from mytable')
```


### pipe (stream)

Sets request to `stream` mode and pulls all rows from all recordsets to a given stream.

__Arguments__

- **stream** - Writable stream in object mode.

__Example__

```javascript
const request = new sql.Request()
request.pipe(stream)
request.query('select * from mytable')
stream.on('error', err => {
    // ...
})
stream.on('finish', () => {
    // ...
})
```

---------------------------------------

### query (command, [callback])

Execute the SQL command. To execute commands like `create procedure` or if you plan to work with local temporary tables, use [batch](#batch-batch-callback) instead.

__Arguments__

- **command** - T-SQL command to be executed.
- **callback(err, recordset)** - A callback which is called after execution has completed, or an error has occurred. Optional. If omitted, returns [Promise](#promises).

__Example__

```javascript
const request = new sql.Request()
request.query('select 1 as number', (err, result) => {
    // ... error checks

    console.log(result.recordset[0].number) // return 1

    // ...
})
```

__Errors__
- ETIMEOUT (`RequestError`) - Request timeout.
- EREQUEST (`RequestError`) - *Message from SQL Server*
- ECANCEL (`RequestError`) - Cancelled.
- ENOCONN (`RequestError`) - No connection is specified for that request.
- ENOTOPEN (`ConnectionError`) - Connection not yet open.
- ECONNCLOSED (`ConnectionError`) - Connection is closed.
- ENOTBEGUN (`TransactionError`) - Transaction has not begun.
- EABORT (`TransactionError`) - Transaction was aborted (by user or because of an error).

```javascript
const request = new sql.Request()
request.query('select 1 as number; select 2 as number', (err, result) => {
    // ... error checks

    console.log(result.recordset[0].number) // return 1
    console.log(result.recordsets[0][0].number) // return 1
    console.log(result.recordsets[1][0].number) // return 2
})
```

**NOTE**: To get number of rows affected by the statement(s), see section [Affected Rows](#affected-rows).

---------------------------------------

### batch (batch, [callback])

Execute the SQL command. Unlike [query](#query-command-callback), it doesn't use `sp_executesql`, so is not likely that SQL Server will reuse the execution plan it generates for the SQL. Use this only in special cases, for example when you need to execute commands like `create procedure` which can't be executed with [query](#query-command-callback) or if you're executing statements longer than 4000 chars on SQL Server 2000. Also you should use this if you're plan to work with local temporary tables ([more information here](http://weblogs.sqlteam.com/mladenp/archive/2006/11/03/17197.aspx)).

NOTE: Table-Valued Parameter (TVP) is not supported in batch.

__Arguments__

- **batch** - T-SQL command to be executed.
- **callback(err, recordset)** - A callback which is called after execution has completed, or an error has occurred. Optional. If omitted, returns [Promise](#promises).

__Example__

```javascript
const request = new sql.Request()
request.batch('create procedure #temporary as select * from table', (err, result) => {
    // ... error checks
})
```

__Errors__
- ETIMEOUT (`RequestError`) - Request timeout.
- EREQUEST (`RequestError`) - *Message from SQL Server*
- ECANCEL (`RequestError`) - Cancelled.
- ENOCONN (`RequestError`) - No connection is specified for that request.
- ENOTOPEN (`ConnectionError`) - Connection not yet open.
- ECONNCLOSED (`ConnectionError`) - Connection is closed.
- ENOTBEGUN (`TransactionError`) - Transaction has not begun.
- EABORT (`TransactionError`) - Transaction was aborted (by user or because of an error).

You can enable multiple recordsets in queries with the `request.multiple = true` command.

---------------------------------------

### bulk (table, [options,] [callback])

Perform a bulk insert.

__Arguments__

- **table** - `sql.Table` instance.
- **options** - Options object to be passed through to driver (currently tedious only). Optional. If argument is a function it will be treated as the callback.
- **callback(err, rowCount)** - A callback which is called after bulk insert has completed, or an error has occurred. Optional. If omitted, returns [Promise](#promises).

__Example__

```javascript
const table = new sql.Table('table_name') // or temporary table, e.g. #temptable
table.create = true
table.columns.add('a', sql.Int, {nullable: true, primary: true})
table.columns.add('b', sql.VarChar(50), {nullable: false})
table.rows.add(777, 'test')

const request = new sql.Request()
request.bulk(table, (err, result) => {
    // ... error checks
})
```

**IMPORTANT**: Always indicate whether the column is nullable or not!

**TIP**: If you set `table.create` to `true`, module will check if the table exists before it start sending data. If it doesn't, it will automatically create it. You can specify primary key columns by setting `primary: true` to column's options. Primary key constraint on multiple columns is supported.

**TIP**: You can also create Table variable from any recordset with `recordset.toTable()`. You can optionally specify table type name in the first argument.

__Errors__
- ENAME (`RequestError`) - Table name must be specified for bulk insert.
- ETIMEOUT (`RequestError`) - Request timeout.
- EREQUEST (`RequestError`) - *Message from SQL Server*
- ECANCEL (`RequestError`) - Cancelled.
- ENOCONN (`RequestError`) - No connection is specified for that request.
- ENOTOPEN (`ConnectionError`) - Connection not yet open.
- ECONNCLOSED (`ConnectionError`) - Connection is closed.
- ENOTBEGUN (`TransactionError`) - Transaction has not begun.
- EABORT (`TransactionError`) - Transaction was aborted (by user or because of an error).

---------------------------------------

### cancel()

Cancel currently executing request. Return `true` if cancellation packet was send successfully.

__Example__

```javascript
const request = new sql.Request()
request.query('waitfor delay \'00:00:05\'; select 1 as number', (err, result) => {
    console.log(err instanceof sql.RequestError)  // true
    console.log(err.message)                      // Cancelled.
    console.log(err.code)                         // ECANCEL

    // ...
})

request.cancel()
```

## Transaction

**IMPORTANT:** always use `Transaction` class to create transactions - it ensures that all your requests are executed on one connection. Once you call `begin`, a single connection is acquired from the connection pool and all subsequent requests (initialized with the `Transaction` object) are executed exclusively on this connection. After you call `commit` or `rollback`, connection is then released back to the connection pool.

```javascript
const transaction = new sql.Transaction(/* [pool] */)
```

If you omit connection argument, global connection is used instead.

__Example__

```javascript
const transaction = new sql.Transaction(/* [pool] */)
transaction.begin(err => {
    // ... error checks

    const request = new sql.Request(transaction)
    request.query('insert into mytable (mycolumn) values (12345)', (err, result) => {
        // ... error checks

        transaction.commit(err => {
            // ... error checks

            console.log("Transaction committed.")
        })
    })
})
```

Transaction can also be created by `const transaction = pool.transaction()`. Requests can also be created by `const request = transaction.request()`.

__Aborted transactions__

This example shows how you should correctly handle transaction errors when `abortTransactionOnError` (`XACT_ABORT`) is enabled. Added in 2.0.

```javascript
const transaction = new sql.Transaction(/* [pool] */)
transaction.begin(err => {
    // ... error checks

    let rolledBack = false

    transaction.on('rollback', aborted => {
        // emited with aborted === true

        rolledBack = true
    })

    new sql.Request(transaction)
    .query('insert into mytable (bitcolumn) values (2)', (err, result) => {
        // insert should fail because of invalid value

        if (err) {
            if (!rolledBack) {
                transaction.rollback(err => {
                    // ... error checks
                })
            }
        } else {
            transaction.commit(err => {
                // ... error checks
            })
        }
    })
})
```

### Events

- **begin** - Dispatched when transaction begin.
- **commit** - Dispatched on successful commit.
- **rollback(aborted)** - Dispatched on successful rollback with an argument determining if the transaction was aborted (by user or because of an error).

---------------------------------------

### begin ([isolationLevel], [callback])

Begin a transaction.

__Arguments__

- **isolationLevel** - Controls the locking and row versioning behavior of TSQL statements issued by a connection. Optional. `READ_COMMITTED` by default. For possible values see `sql.ISOLATION_LEVEL`.
- **callback(err)** - A callback which is called after transaction has began, or an error has occurred. Optional. If omitted, returns [Promise](#promises).

__Example__

```javascript
const transaction = new sql.Transaction()
transaction.begin(err => {
    // ... error checks
})
```

__Errors__
- ENOTOPEN (`ConnectionError`) - Connection not yet open.
- EALREADYBEGUN (`TransactionError`) - Transaction has already begun.

---------------------------------------

### commit ([callback])

Commit a transaction.

__Arguments__

- **callback(err)** - A callback which is called after transaction has committed, or an error has occurred. Optional. If omitted, returns [Promise](#promises).

__Example__

```javascript
const transaction = new sql.Transaction()
transaction.begin(err => {
    // ... error checks

    transaction.commit(err => {
        // ... error checks
    })
})
```

__Errors__
- ENOTBEGUN (`TransactionError`) - Transaction has not begun.
- EREQINPROG (`TransactionError`) - Can't commit transaction. There is a request in progress.

---------------------------------------

### rollback ([callback])

Rollback a transaction. If the queue isn't empty, all queued requests will be Cancelled and the transaction will be marked as aborted.

__Arguments__

- **callback(err)** - A callback which is called after transaction has rolled back, or an error has occurred. Optional. If omitted, returns [Promise](#promises).

__Example__

```javascript
const transaction = new sql.Transaction()
transaction.begin(err => {
    // ... error checks

    transaction.rollback(err => {
        // ... error checks
    })
})
```

__Errors__
- ENOTBEGUN (`TransactionError`) - Transaction has not begun.
- EREQINPROG (`TransactionError`) - Can't rollback transaction. There is a request in progress.

## Prepared Statement

**IMPORTANT:** always use `PreparedStatement` class to create prepared statements - it ensures that all your executions of prepared statement are executed on one connection. Once you call `prepare`, a single connection is acquired from the connection pool and all subsequent executions are executed exclusively on this connection. After you call `unprepare`, the connection is then released back to the connection pool.

```javascript
const ps = new sql.PreparedStatement(/* [pool] */)
```

If you omit the connection argument, the global connection is used instead.

__Example__

```javascript
const ps = new sql.PreparedStatement(/* [pool] */)
ps.input('param', sql.Int)
ps.prepare('select @param as value', err => {
    // ... error checks

    ps.execute({param: 12345}, (err, result) => {
        // ... error checks

        // release the connection after queries are executed
        ps.unprepare(err => {
            // ... error checks

        })
    })
})
```

**IMPORTANT**: Remember that each prepared statement means one reserved connection from the pool. Don't forget to unprepare a prepared statement when you've finished your queries!

You can execute multiple queries against the same prepared statement but you *must* unprepare the statement when you have finished using it otherwise you will cause the connection pool to run out of available connections.

**TIP**: You can also create prepared statements in transactions (`new sql.PreparedStatement(transaction)`), but keep in mind you can't execute other requests in the transaction until you call `unprepare`.

---------------------------------------

### input (name, type)

Add an input parameter to the prepared statement.

__Arguments__

- **name** - Name of the input parameter without @ char.
- **type** - SQL data type of input parameter.

__Example__

```javascript
ps.input('input_parameter', sql.Int)
ps.input('input_parameter', sql.VarChar(50))
```

__Errors__ (synchronous)
- EARGS (`PreparedStatementError`) - Invalid number of arguments.
- EINJECT (`PreparedStatementError`) - SQL injection warning.

---------------------------------------

### output (name, type)

Add an output parameter to the prepared statement.

__Arguments__

- **name** - Name of the output parameter without @ char.
- **type** - SQL data type of output parameter.

__Example__

```javascript
ps.output('output_parameter', sql.Int)
ps.output('output_parameter', sql.VarChar(50))
```

__Errors__ (synchronous)
- EARGS (`PreparedStatementError`) - Invalid number of arguments.
- EINJECT (`PreparedStatementError`) - SQL injection warning.

---------------------------------------

### prepare (statement, [callback])

Prepare a statement.

__Arguments__

- **statement** - T-SQL statement to prepare.
- **callback(err)** - A callback which is called after preparation has completed, or an error has occurred. Optional. If omitted, returns [Promise](#promises).

__Example__

```javascript
const ps = new sql.PreparedStatement()
ps.prepare('select @param as value', err => {
    // ... error checks
})
```

__Errors__
- ENOTOPEN (`ConnectionError`) - Connection not yet open.
- EALREADYPREPARED (`PreparedStatementError`) - Statement is already prepared.
- ENOTBEGUN (`TransactionError`) - Transaction has not begun.

---------------------------------------

### execute (values, [callback])

Execute a prepared statement.

__Arguments__

- **values** - An object whose names correspond to the names of parameters that were added to the prepared statement before it was prepared.
- **callback(err)** - A callback which is called after execution has completed, or an error has occurred. Optional. If omitted, returns [Promise](#promises).

__Example__

```javascript
const ps = new sql.PreparedStatement()
ps.input('param', sql.Int)
ps.prepare('select @param as value', err => {
    // ... error checks

    ps.execute({param: 12345}, (err, result) => {
        // ... error checks

        console.log(result.recordset[0].value) // return 12345
        console.log(result.rowsAffected) // Returns number of affected rows in case of INSERT, UPDATE or DELETE statement.

        ps.unprepare(err => {
            // ... error checks
        })
    })
})
```

You can also stream executed request.

```javascript
const ps = new sql.PreparedStatement()
ps.input('param', sql.Int)
ps.prepare('select @param as value', err => {
    // ... error checks

    ps.stream = true
    const request = ps.execute({param: 12345})

    request.on('recordset', columns => {
        // Emitted once for each recordset in a query
    })

    request.on('row', row => {
        // Emitted for each row in a recordset
    })

    request.on('error', err => {
        // May be emitted multiple times
    })

    request.on('done', result => {
        // Always emitted as the last one

        console.log(result.rowsAffected) // Returns number of affected rows in case of INSERT, UPDATE or DELETE statement.

        ps.unprepare(err => {
            // ... error checks
        })
    })
})
```

**TIP**: To learn more about how number of affected rows works, see section [Affected Rows](#affected-rows).

__Errors__
- ENOTPREPARED (`PreparedStatementError`) - Statement is not prepared.
- ETIMEOUT (`RequestError`) - Request timeout.
- EREQUEST (`RequestError`) - *Message from SQL Server*
- ECANCEL (`RequestError`) - Cancelled.

---------------------------------------

### unprepare ([callback])

Unprepare a prepared statement.

__Arguments__

- **callback(err)** - A callback which is called after unpreparation has completed, or an error has occurred. Optional. If omitted, returns [Promise](#promises).

__Example__

```javascript
const ps = new sql.PreparedStatement()
ps.input('param', sql.Int)
ps.prepare('select @param as value', err => {
    // ... error checks

    ps.unprepare(err => {
        // ... error checks

    })
})
```

__Errors__
- ENOTPREPARED (`PreparedStatementError`) - Statement is not prepared.

## CLI

If you want to add the MSSQL CLI tool to your path, you must install it globally with `npm install -g mssql`.

__Setup__

Create a `.mssql.json` configuration file (anywhere). S