Recall

• When to use group by?• Difference between ‘having’ and

‘where’?• Difference between scalar and

aggregate functions?• What are the different types of

joins?

Introduction To DBMS and MySQLStored Procedures

Week 6 – Day1

Stored Procedures

• A stored procedure is a method to encapsulate repetitive tasks.

• A stored Procedure is actually stored in database data dictionary

Without Stored Procedure

Employee.jsp......................

Select * from tbl_employee ................

Report.php..........................

Select * from tbl_employee .................

.....................Select * from tbl_employee

viewDetails.php...................................................

Select * from tbl_employee

...............Database

Select * from tbl_employee

Select * from tbl_employee

Select * from tbl_employee

Stored Procedure

Employee.php....................................................Call getName();

................

Report.php............................................................................. Call getName();

viewDetails.php...................................................Call getName();

...............

getName()BeginSelect * from tbl_employee End

Database

Advantages• Precompiled Execution

• Mysql compiles each stored procedure once and then reutilizes the execution plan. This result in tremendous performance boosts when stored procedures are called repeatedly

• Reduced client server traffic• If network traffic is concerned you will be happy to learn that stored procedures can reduce long sql queries to a single line that is transmitted between application program and database server.

Advantages• Efficient reuse of code and programming

abstraction• Stored procedures can be used by multiple programs and users. If you utilize them in a planned manner, you’ll find the development cycle takes less time.

• Enhanced Security Control• You can grant users permission to execute stored procedure independently of underlying table permissions

How to create Stored Procedure ? example

Delimiter //CREATE PROCEDURE getName(IN id int)

BEGINSelect * from tbl_user where userid=id;

ENDDelimiter ;

Call getName(‘1001’);

How to create Stored Procedure ? example

Delimiter //CREATE PROCEDURE getName(IN id int)

BEGINSelect * from tbl_user where userid=id;

END//Delimiter ;

Call getName(‘1001’);

By default the delimiter is “;” . That means if you want the sever to start compiling of your sql query, you must put “;” and then press “enter”.

Delimiter // statement changes the default delimiter to “//” so that giving “;” inside store procedure will not push server to start compilation

How to create Stored Procedure ? example

Delimiter //CREATE PROCEDURE getName(IN id int)

BEGINSelect * from tbl_user where userid=id;

END//Delimiter ;

Call getName(‘1001’);

Is the keyword to create a new stored procedure

How to create Stored Procedure ? example

Delimiter //CREATE PROCEDURE getName(IN id int)

BEGINSelect * from tbl_user where userid=id;

END//Delimiter ;

Call getName(‘1001’);

Is the name of the stored procedure that we are creating

How to create Stored Procedure ? example

Delimiter //CREATE PROCEDURE getName ( IN id

int)BEGIN

Select * from tbl_user where userid=id;

END//Delimiter ;

Call getName(‘1001’);

Is the parameter list (here intiger type variable called “id”)

IN -> passing value into the stored procedure

Out -> returning value out of stored procedure

INOUT -> Same variable can be used to send in and out of stored procedure

How to create Stored Procedure ? example

Delimiter //CREATE PROCEDURE getName ( IN id

int)BEGIN

Select * from tbl_user where userid=id;

END//Delimiter ;

Call getName(‘1001’);

Is the keyword to begin the block of codes inside the stored functionIt’s same as curly brace ‘{‘ we use for functions in C

How to create Stored Procedure ? example

Delimiter //CREATE PROCEDURE getName ( IN id

int)BEGIN

Select * from tbl_user where userid=id;

END//Delimiter ;

Call getName(‘1001’);

Is the body of the stored procedure. Here we have only a single select query statements. We can also apply logic using the below • DECLARE a INT; : declaring an integer

type variable

• SET a=20; : Setting value of a to 20

• IF THEN• ELSE IF

label1: LOOP SET p1 = p1 + 1; IF p1 < 10 THEN ITERATE label1; END IF; LEAVE label1; END LOOP label1;

: For conditions

: Loops

How to create Stored Procedure ? example

Delimiter //CREATE PROCEDURE getName ( IN id

int)BEGIN

Select * from tbl_user where userid=id;

END//Delimiter ;

Call getName(‘1001’);

End // -> the compiler starts compiling after you press enter. This is because “//” is the delimiter

How to create Stored Procedure ? example

Delimiter //CREATE PROCEDURE getName ( IN id

int)BEGIN

Select * from tbl_user where userid=id;

END//Delimiter ;

Call getName(‘1001’);

Now we are changing the delimiter back to “;”

How to create Stored Procedure ? example

Delimiter //CREATE PROCEDURE getName ( IN id

int)BEGIN

Select * from tbl_user where userid=id;

END//Delimiter ;

Call getName(‘1001’);

Calling the stored procedure we’ve just created and passing the value 1001 as its argument

How to create Stored Procedure ? example

Delimiter //CREATE PROCEDURE getSale ( IN id

int,OUT sale int,OUT aver int)BEGIN

Select sum(price) into sale,avg(price) into aver from tbl_purchase where deptid=id;

END//Delimiter ;

Call getSale(1001,@sale,@aver);Select @sale;Select @aver;

• Create the below table

• Create a stored procedure called – csp_getSalary(1000) : should return the

salary of employee with id as passed in the argument

– Csp_getSalaryAtPlace(‘calicut’,@total) : should return the total salary of employees from a perticular place

Live Task

Tbl_employeeEmp_id Emp_name Emp_age Emp_email int_salary vchr_place

1000 Deepak 24 dk@gmail.com 10000 Calicut

1001 Aneesh 23 an@gmail.com 20000 Cochin

1002 Naveen 25 nn@gmail.com 10000 Calicut

1003 Jacob 25 jb@gmail.com 30000 Cochin

Cursors

• SELECT INTO is fine for single-row queries, but many applications require the querying of multiple rows of data. You will use a cursor in MySQL to accomplish this.

• A cursor lets you fetch one or more rows from a SQL result set into stored program variables, usually with the intention of performing some row-by-row processing on the result set.

Cursors - exampleCreate procedure changePlace()Begin

DECLARE empId INT;DECLARE placeId VARCHAR(50);DECLARE done INT DEFAULT 0;DECLARE myCur CURSOR FOR SELECT emp_id,vchr_place from tbl_employees;DECLARE CONTINUE HANDLER FOR NOT FOUND SET done=1;OPEN myCur;Emp_Loop: LOOPFETCH myCur INTO empId, placeId;If done=1 THENLEAVE Emp_loopElse iterate emp_loopENDIFEND LOOP emp_loopCLOSE myCur ;

END//

Declare Handler• The DECLARE ... HANDLER statement

specifies a handler that deals with one or more conditions. If one of these conditions occurs, the specified statement executes.

• DECLARE handler_action HANDLER FOR condition_value [, condition_value] ... Statement

– handler_action: – CONTINUE | EXIT | UNDO

– condition_value: mysql_error_code – SQLWARNING | NOT FOUND | SQLEXCEPTION

Questions?“A good question deserve a

good grade…”

Self Check !!

• Why should someone use stored procedure?

–To avoid data redundancy–To reduce network traffic between

application server and database server–To ensure data integrity

Self Check !!

• Why should someone use stored procedure?

–To avoid data redundancy–To reduce network traffic between

application server and database server–To ensure data integrity

Self Check !!

Self Check !!

• Why should someone change the delimiter before creating a stored procedure?

– To use ; as seperation between multiple statements in a stored procedure body

– To push the server to compile the whole body of stored procedure all together

– Both of above– None of above

Self Check !!

• Why should someone change the delimiter before creating a stored procedure?

– To use ; as seperation between multiple statements in a stored procedure body

– To push the server to compile the whole body of stored procedure all together

– Both of above– None of above

Self Check !!

CREATE PROCEDURE simpleProc ( OUT param1 INT)

BEGIN SELECT COUNT(*) INTO param1 FROM

t ;END

CALL simpleProc(@a);Select @a ;

Self Check !!

CREATE PROCEDURE simpleProc ( OUT param1 INT)

BEGIN SELECT COUNT(*) INTO param1 FROM

t ;END

CALL simpleProc(@a);Select @a ;

Self Check !!

•What are the uses of cursors?

• For extracting multiple rows from a table• For extracting multiple rows into variables from a table• For setting handlers

Self Check !!

•What are the uses of cursors?

• For extracting multiple rows from a table• For extracting multiple rows into variables from a table• For setting handlers

End of day