Stored Procedures in Sql

Stored Procedures are created to perform one or more DML operations on Database.

 It is nothing but the group of SQL statements that accepts some input in the form of parameters and performs some task and may or may not returns a value.

Syntax :

CREATE or REPLACE PROCEDURE name(parameters)

IS

variables;

BEGIN

//statements;

END;

The most important part is parameters. Parameters are used to pass values to the Procedure. 

There are 3 different types of parameters, they are as follows:

IN:

This is the Default Parameter for the procedure. It always recieves the values from calling program.

OUT:

This parameter always sends the values to the calling program.

IN OUT:

This parameter performs both the operations. It Receives value from as well as sends the values to the calling program.

CREATE or REPLACE PROCEDURE INC_SAL(eno IN NUMBER, up_sal OUT NUMBER)

IS

BEGIN

UPDATE emp_table SET salary = salary+1000 WHERE emp_no = eno;

COMMIT;

SELECT sal INTO up_sal FROM emp_table WHERE emp_no = eno;

END; 

Steps to execute the procedure:

>Declare a Variable to Store the value comming out from Procedure :

VARIABLE v NUMBER;

>Execution of the Procedure:

EXECUTE INC_SAL(1002, :v);

>To check the updated salary use SELECT statement:

 SELECT * FROM emp_table WHERE emp_no = 1002;

or Use print statement :

PRINT :v

Example For Stored Procedures with Multiple Parameters:

CREATE PROCEDURE SelectAllCustomers @City nvarchar(30), @PostalCode nvarchar(10)

AS

SELECT * FROM Customers WHERE City = @City AND PostalCode = @PostalCode

GO;

Execution of Stored Procedures in SQL 

EXEC SelectAllCustomers City = "London", PostalCode = "WA1 1DP";

Example For Stored Procedure with One Parameter:

Example of SQL Stored Procedure with one parameter- 

CREATE PROCEDURE SelectAllCustomers @City nvarchar(30)

AS

SELECT * FROM Customers WHERE City = @City

GO;

Execution of Stored Procedures in SQL –

EXEC SelectAllCustomers City = "London";