What is a stored procedure?
Stored procedures are a batch of SQL statements that can be executed in a couple of ways. Most major DBMs support stored procedures; however, not all do. You will need to verify with your particular DBMS help documentation for specifics. As I am most familiar with SQL Server I will use that as my samples.
To create a stored procedure the syntax is fairly simple:
CREATE PROCEDURE <owner>.<procedure name> <Param> <datatype>AS <Body>So for example:
CREATE PROCEDURE Users_GetUserInfo @login nvarchar(30)=nullAS SELECT * from [Users] WHERE ISNULL(@login,login)=loginA benefit of stored procedures is that you can centralize data access logic into a single place that is then easy for DBA's to optimize. Stored procedures also have a security benefit in that you can grant execute rights to a stored procedure but the user will not need to have read/write permissions on the underlying tables. This is a good first step against SQL injection.
Stored procedures do come with downsides, basically the maintenance associated with your basic CRUD operation. Let's say for each table you have an Insert, Update, Delete and at least one select based on the primary key, that means each table will have 4 procedures. Now take a decent size database of 400 tables, and you have 1600 procedures! And that's assuming you don't have duplicates which you probably will.
This is where using an ORM or some other method to auto generate your basic CRUD operations has a ton of merit.
A stored procedure is a set of precompiled SQL statements that are used to perform a special task.
Example: If I have an Employee table
Employee ID Name Age Mobile---------------------------------------001 Sidheswar 25 9938885469002 Pritish 32 9178542436First I am retrieving the Employee table:
Create Procedure Employee detailsAsBegin Select * from EmployeeEndTo run the procedure on SQL Server:
Execute Employee details--- (Employee details is a user defined name, give a name as you want)Then second, I am inserting the value into the Employee Table
Create Procedure employee_insert (@EmployeeID int, @Name Varchar(30), @Age int, @Mobile int)AsBegin Insert Into Employee Values (@EmployeeID, @Name, @Age, @Mobile)EndTo run the parametrized procedure on SQL Server:
Execute employee_insert 003,’xyz’,27,1234567890 --(Parameter size must be same as declared column size)Example: @Name Varchar(30)
In the Employee table the Name column's size must be varchar(30).
A stored procedure is a group of SQL statements that has been created and stored in the database. A stored procedure will accept input parameters so that a single procedure can be used over the network by several clients using different input data. A stored procedures will reduce network traffic and increase the performance. If we modify a stored procedure all the clients will get the updated stored procedure.
Sample of creating a stored procedure
CREATE PROCEDURE test_displayAS SELECT FirstName, LastName FROM tb_test;EXEC test_display;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.
A stored procedure allows faster execution.
If the operation requires a large amount of SQL code that 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 a 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.
A 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.
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.
In SQL Server we have different types of stored procedures:
- System stored procedures
- User-defined stored procedures
- Extended stored Procedures
System-stored procedures are stored in the master database and these start with a
sp_prefix. These procedures can be used to perform a variety of tasks to support SQL Server functions for external application calls in the system tablesExample: sp_helptext [StoredProcedure_Name]
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 the
sp_prefix because if we use thesp_prefix first, it will check the master database, and then it comes to user defined database.Extended stored procedures are the procedures that call functions from DLL files. Nowadays, extended stored procedures are deprecated for the reason it would be better to avoid using extended stored procedures.