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STORED PROCEDURE WITH

CURSORS

Jaseena A Pjsnp65@gmail.comwww.facebook.com/Jaseena

Muhammed A Ptwitter.com/usernamein.linkedin.com/in/profilename9539443588

WHAT IS STORED PROCEDURE? A stored procedure is a subroutine available to applications that

access a relational database system.

Extensive or complex processing that requires execution of several SQL statements is moved into stored procedures, and all applications call the procedures.

Typical uses for stored procedures include data validation (integrated into the database) or access control mechanisms.

Stored procedures can consolidate and centralize logic that was originally implemented in applications.

WHY WE USE STORED PROCEDURE Stored procedures should run faster

-Once created, stored procedures are compiled and stored in the data base. Saving resources

-code is stored in a pre-compiled form ;syntactically valid and does not need to be compiled again.

Improving the scalability of applications-each user of the stored procedure will use exactly the

same form of queries that means the code is reused.

WHY WE USE STORED PROCEDURE

Less network traffic-instead of sending multiple lengthy SQL

statements, the application has to send only name and parameters of the stored procedure.

Stored procedures are secure.- Database administrator can grant

appropriate permissions to applications that access stored procedures in the database without giving any permission on the underlying database tables.

LIMITATIONS OF STORED PROCEDURE For a lot of stored procedures, the memory usage of every

connection will increase substantially.

Overuse a large number of logical operations inside store procedures, the CPU usage will also increase because database server is not well-designed for logical operations.

A constructs of stored procedures make it more difficult to develop stored procedures that have complicated business logic.

It is difficult to debug stored procedures. Only few database management systems allow you to debug stored procedures

It is not easy to develop and maintain stored procedures; Required specialized skill set that not all application developers possess

Working with SPMysql> CREATE DATABASE my_db; Mysql>USE my_db;

Mysql>CREATE TABLE Tbl_student(RollNo int,Name varchar(20));

Mysql> INSERT INTO Tbl_student VALUES (1,’Dilna’),(2,’Diya’),(3,’Dinan’);

Mysql>SELECT * FROM Tbl_student;

+--------+-------+| RollNo | Name |+--------+-------+| 1 | Dilna || 2 | Diya || 3 | Dinan |+--------+-------+

Working with SPMusql>delimiter //

Mysql> CREATE PROCEDURE proc1 () BEGIN

DECLARE a INT; SET a = 3; INSERT INTO Tbl_student VALUES (5,’Name’); SELECT * FROM Tbl_student WHERE RollNo=a;

END; //Mysql>delimiter ;

Mysql>call proc1();

DEFAULT 0

+--------+-------+| RollNo | Name |+--------+-------+| 3 | Dinan |+--------+-------+

Working with SP-parameter passing CREATE PROCEDURE proc.Name() ...

CREATE PROCEDURE proc.Name ([IN] name data-type) ... CREATE PROCEDURE proc.Name (OUT name data-type) ... CREATE PROCEDURE proc.Name (INOUT name data-type)

Working with SP-parameter passing

CREATE PROCEDURE proc1 (OUT count int) BEGIN

DECLARE a INT; SET a = 3; INSERT INTO Tbl_student VALUES (5,’Name’); SELECT count(RollNo) into countFROM Tbl_student ;

END; //Mysql>call proc1(@count);

Mysql>select @count;+--------+| @count |+--------+| 4 |+--------+

Conditions and If-then-elseMysql>alter table Tbl_student add Grade varchar(10); Mysql> delimiter //

Mysql> create procedure proc3(IN mrk int,IN rlno int) BEGIN if mrk>90 then update Tbl_student set Grade=‘A’ where RollNo=rlno; end if; end//Mysql> delimiter //

Mysql>call proc3(95,1);

Mysql>select * from Tbl_student;

+--------+-------+-------+| RollNo | Name | Grade |+--------+-------+-------+| 1 | Dilna | A || 2 | Diya | NULL || 3 | Dinan | NULL || 5 | Name | NULL |+--------+-------+-------+

CASEMysql>create procedure proc4(IN mrk int,IN rlno int) begin case mrk when 90 then update Tbl_student set Grade=‘A’ where RollNo=rlno; when 80 then update Tbl_student set Grade='B' where RollNo=rlno; else update Tbl_student set Grade='C' where RollNo=rlno; end case; end;//Mysql>call proc4(2,80);Mysql>call proc5(3,70);Mysql>select * from Tbl_student;

+--------+-------+-------+| RollNo | Name | Grade |+--------+-------+-------+| 1 | Dilna | A || 2 | Diya | B || 3 | Dinan | C || 5 | Name | NULL |+--------+-------+-------+

WHILEmysql> create procedure proc6() begin declare v int; set v=0; create table student(count int); while v<5 do insert into student(count) values(v); set v=v+1; end while; end;//mysql> call proc6();mysql> select * from student;

+-------+| count |+-------+| 0 || 1 || 2 || 3 || 4 |+-------+

REPEAT

mysql>create procedure proc9() begin declare v int; set v=0; create table value(v1 int); repeat insert into value values (v); set v=v+1; until v>=5 end repeat; end;//mysql> call proc9();

mysql> select * from value;

+------+| v1 |+------+| 0 || 1 || 2 || 3 || 4 |+------+

LOOPCREATE PROCEDURE p16 ()

BEGIN DECLARE v INT; SET v = 0; loop_label: LOOP INSERT INTO t VALUES (v); SET v = v + 1; IF v >= 5 THEN LEAVE loop_label; END IF;

END LOOP; END; //

The LEAVE statement means "exit the loop". The actual syntax of the LEAVE statement is the word LEAVE and a statement label.

CURSOR IN MYSQL A cursor allows us to 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.

A cursor has the following properties:

Asensitive: The server may or may not make a copy of its result table

Read only: Not updatable Nonscrollable: Can be traversed only in one direction and

cannot skip rows

HOW CURSOR WORKS?

CURSORS create procedure my_proc(OUT return_val int) begin declare b int; declare a int default 1; declare mycur_1 cursor for select pk_student_id from Tbl_student; declare continue handler for not found set a=0; open mycur_1; repeat fetch mycur_1 into b; set return_val=b; until a=0 end repeat; close mycur_1; end;//

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