> A stored procedure is a group of Sql statements that has been created and stored in the database. Stored procedure will accept input parameters so that a single procedure can be used over the network by several clients using different input data. Stored procedure will reduce network traffic and increase the performance. If we modify stored procedure all the clients will get the updated stored procedure
In SQL we are having different types of stored procedures are there
a) System Stored Procedures
b) User Defined Stored procedures
c) Extended Stored Procedures
System Stored Procedures:
System stored procedures are stored in the master database and these are starts with a sp_ prefix. These procedures can be used to perform variety of tasks to support Sql server functions for external application calls in the system tables and use to perform many administrative and informational activities.
Ex: sp_helptext [StoredProcedure_Name]
User Defined Stored Procedures:
User Defined stored procedures are usually stored in a user database and are typically designed to complete the tasks in the user database. While coding these procedures don’t use sp_ prefix because if we use the sp_ prefix first it will check master database then it comes to user defined database.
Stored procedure are modules or routines that encapsulate code for reuse. A stored procedures can take input parameters, return tabular or scalar results and messages to the client.
Extended Stored Procedures:
Extended stored procedures are the procedures that call functions from DLL files that an instance of Microsoft SQL Server can dynamically load and run. Now a day’s extended stored procedures are depreciated for that reason it would be better to avoid using of Extended Stored procedures.
Why use Stored Procedures?
> Rewriting inline SQL statements as Stored Procedures
> Compilation and storing of the query execution plan
> Enabling of conditional and procedural logic
> Centralized repository for DML and DDL code enabling code reuse
> Protection from SQL Injection attacks
> Enabling of strict security model
> Readability
Sample of creating Stored Procedure
USE AdventureWorks2008R2;
GO
CREATE PROCEDURE dbo.sp_who
AS
SELECT FirstName, LastName FROM Person.Person;
GO
EXEC sp_who;
EXEC dbo.sp_who;
GO
DROP PROCEDURE dbo.sp_who;
GO
Advantages of using stored procedures
a) Stored procedure allows modular programming.
You can create the procedure once, store it in the database, and call it any number of times in your program.
b) Stored Procedure allows faster execution.
If the operation requires a large amount of SQL code is performed repetitively, stored procedures can be faster. They are parsed and optimized when they are first executed, and a compiled version of the stored procedure remains in memory cache for later use. This means the stored procedure does not need to be reparsed and reoptimized with each use resulting in much faster execution times.
c) Stored Procedure 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.
d) Stored procedures provide better security to your data
Users can be granted permission to execute a stored procedure even if they do not have permission to execute the procedure's statements directly.