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How to: Perform Transactions

SQL Server 2008 R2

The SQLSRV driver of the Microsoft Drivers for PHP for SQL Server provides three functions for performing transactions:

The PDO_SQLSRV driver provides three methods for performing transactions:

See PDO::beginTransaction for an example.

The remainder of this topic explains and demonstrates how to use the SQLSRV driver to perform transactions.

The steps to execute a transaction can be summarized as follows:

  1. Begin the transaction with sqlsrv_begin_transaction.

  2. Check the success or failure of each query that is part of the transaction.

  3. If appropriate, commit the transaction with sqlsrv_commit. Otherwise, roll back the transaction with sqlsrv_rollback. After calling sqlsrv_commit or sqlsrv_rollback, the driver is returned to auto-commit mode.

    By default, the Microsoft Drivers for PHP for SQL Server is in auto-commit mode. This means that all queries are automatically committed upon success unless they have been designated as part of an explicit transaction by using sqlsrv_begin_transaction.

    If an explicit transaction is not committed with sqlsrv_commit, it will be rolled back upon closing of the connection or termination of the script.

    Do not use embedded Transact-SQL to perform transactions. For example, do not execute a statement with "BEGIN TRANSACTION" as the Transact-SQL query to begin a transaction. The expected transactional behavior cannot be guaranteed when you use embedded Transact-SQL to perform transactions.

    The sqlsrv functions listed earlier should be used to perform transactions.

Description

The following example executes several queries as part of a transaction. If all the queries are successful, the transaction is committed. If any one of the queries fails, the transaction is rolled back.

The example tries to delete a sales order from the Sales.SalesOrderDetail table and adjust product inventory levels in the Product.ProductInventory table for each product in the sales order. These queries are included in a transaction because all queries must be successful for the database to accurately reflect the state of orders and product availability.

The first query in the example retrieves product IDs and quantities for a specified sales order ID. This query is not part of the transaction. However, the script ends if this query fails because the product IDs and quantities are required to complete queries that are part of the subsequent transaction.

The ensuing queries (deletion of the sales order and updating of the product inventory quantities) are part of the transaction.

The example assumes that SQL Server and the AdventureWorks database are installed on the local computer. All output is written to the console when the example is run from the command line.

Code

<?php
/* Connect to the local server using Windows Authentication and
specify the AdventureWorks database as the database in use. */
$serverName = "(local)";
$connectionInfo = array( "Database"=>"AdventureWorks");
$conn = sqlsrv_connect( $serverName, $connectionInfo);
if( $conn === false )
{
     echo "Could not connect.\n";
     die( print_r( sqlsrv_errors(), true));
}

/* Begin transaction. */
if( sqlsrv_begin_transaction($conn) === false ) 
{ 
     echo "Could not begin transaction.\n";
     die( print_r( sqlsrv_errors(), true));
}

/* Set the Order ID.  */
$orderId = 43667;

/* Execute operations that are part of the transaction. Commit on
success, roll back on failure. */
if (perform_trans_ops($conn, $orderId))
{
     //If commit fails, roll back the transaction.
     if(sqlsrv_commit($conn))
     {
         echo "Transaction committed.\n";
     }
     else
     {
         echo "Commit failed - rolling back.\n";
         sqlsrv_rollback($conn);
     }
}
else
{
     "Error in transaction operation - rolling back.\n";
     sqlsrv_rollback($conn);
}

/*Free connection resources*/
sqlsrv_close( $conn);

/*----------------  FUNCTION: perform_trans_ops  -----------------*/
function perform_trans_ops($conn, $orderId)
{
    /* Define query to update inventory based on sales order info. */
    $tsql1 = "UPDATE Production.ProductInventory 
              SET Quantity = Quantity + s.OrderQty 
              FROM Production.ProductInventory p 
              JOIN Sales.SalesOrderDetail s 
              ON s.ProductID = p.ProductID 
              WHERE s.SalesOrderID = ?";

    /* Define the parameters array. */
    $params = array($orderId);

    /* Execute the UPDATE statement. Return false on failure. */
    if( sqlsrv_query( $conn, $tsql1, $params) === false ) return false;

    /* Delete the sales order. Return false on failure */
    $tsql2 = "DELETE FROM Sales.SalesOrderDetail 
              WHERE SalesOrderID = ?";
    if(sqlsrv_query( $conn, $tsql2, $params) === false ) return false;

    /* Return true because all operations were successful. */
    return true;
}
?>

Comments

For the purpose of focusing on transaction behavior, some recommended error handling is not included in the previous example. For a production application, we recommend that any call to a sqlsrv function be checked for errors and handled accordingly.

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