Stored Procedures

When you create an application with Microsoft® SQL Server™, the Transact-SQL programming language is the primary programming interface between your applications and the SQL Server database. When you use Transact-SQL programs, two methods are available for storing and executing the programs. You can store the programs locally and create applications that send the commands to SQL Server and process the results, or you can store the programs as stored procedures in SQL Server and create applications that execute the stored procedures and process the results.

Stored procedures in SQL Server are similar to procedures in other programming languages in that they can:

• Accept input parameters and return multiple values in the form of output parameters to the calling procedure or batch.
• Contain programming statements that perform operations in the database, including calling other procedures.
• Return a status value to a calling procedure or batch to indicate success or failure (and the reason for failure).

You can use the Transact-SQL EXECUTE statement to run a stored procedure. Stored procedures are different from functions in that they do not return values in place of their names and they cannot be used directly in an expression.

The benefits of using stored procedures in SQL Server rather than Transact-SQL programs stored locally on client computers are:

• They allow modular programming.

  You can create the procedure once, store it in the database, and call it any number of times in your program. Stored procedures can be created by a person who specializes in database programming, and they can be modified independently of the program source code.

• They allow faster execution.

  If the operation requires a large amount of Transact-SQL code or is performed repetitively, stored procedures can be faster than batches of Transact-SQL code. They are parsed and optimized when they are created, and an in-memory version of the procedure can be used after the procedure is executed the first time. Transact-SQL statements repeatedly sent from the client each time they run are compiled and optimized every time they are executed by SQL Server.

• They can reduce network traffic.

  An operation requiring hundreds of lines of Transact-SQL code can be performed through a single statement that executes the code in a procedure, rather than by sending hundreds of lines of code over the network.

• They can be used as a security mechanism.

  Users can be granted permission to execute a stored procedure even if they do not have permission to execute the procedure’s statements directly.

A SQL Server stored procedure is created with the Transact-SQL CREATE PROCEDURE statement and can be modified with the ALTER PROCEDURE statement. The stored procedure definition contains two primary components: the specification of the procedure name and its parameters, and the body of the procedure, which contains Transact-SQL statements that perform the procedure’s operations.

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