Stored procedures, cursors, and transactions in MySQL are discussed. Key points: - Stored procedures allow encapsulating repetitive tasks and are compiled only once for improved efficiency. Syntax and examples of creating and calling stored procedures are provided. - Cursors enable iterating over database records sequentially. Syntax for declaring, opening, fetching, and closing cursors is explained. - Transactions ensure data integrity by allowing a set of SQL statements to be treated as a single unit that must fully commit or roll back. The ACID properties of transactions - atomicity, consistency, isolation, and durability - are defined. Examples of using transactions with stored procedures and cursors are given.

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STORED PROCEDURE,CURSOR AND
TRANSACTIONS IN MySQL

3. Disclaimer: This presentation is prepared by trainees of
baabtra.com as a part of mentoring program. This is not
official document of baabtra.com – Mentoring Partner

4. STORED PROCEDURE
• A stored procedure is a method to encapsulate repetitive
tasks.
• A stored Procedure is actually stored in database data
dictionary.
• Can call and run from Database Environment
• Compiles only one time

5. Syntax:
DELIMITER //
CREATE PROCEDURE ProcedureName (MODE
Parameters Datatype) BEGIN
SQL Statements;
END //

6. Example :
delimiter //
CREATE PROCEDURE csp_gettotalsalaryatplace
(IN place varchar(20),OUT total int)
BEGIN
select sum(int_salary) into total from tbl_employee where
vchr_place=‘Mexico’;
END //

7. CALLING A Stored Procedure
CALL csp_ProcedureName(Parameters);
Example:
CALL csp_gettotalsalryatplace(‘Calicut’,@total);
select @total;

8. ADVANTAGES OF SP
• Pre-Compiled Execution : The Server compiles the SP
only once and Re-utilize it
• Reduced Client-Server Traffic : SP reduces the traffic
from Client by sending short SP calling statements
instead of whole vast SQL statements
• Efficient Re-Usability of Code : Once a SP stored in the
Database, it can be used by several Client Programs

9. CURSOR
• Control Structure that enables iterations over the records in a
Database
• Used to process individual Rows returned by the Queries
• It enables the rows in a result set to be processed sequentially
• It can be viewed as a pointer to one row in a set of rows
• Cursor can refer one Row at a time, but can be moved through the
Row Set

10. Synatx :
• Declaring a Cursor by DECLARE statement. Variable declaration must be done before
the declaration of the Cursor
DECLARE cursor_name CURSOR FOR SELECT_statement;
• OPEN : Opens a Cursor, that means, initializes the Result set (Row set) for the Cursor
OPEN cursor_name;
• FETCH : To retrieve the next Row pointed by the Cursor and move the Cursor to the
next Row in the Result set
FETCH cursor_name INTO variables list;
• CLOSE : When Cursor is no longer used, it must be closed
CLOSE cursor_name;

11. DATABASE TRANSACTIONS
? WHAT IS DATABASE TRANSACTIONS
• A database transactions is a unit of work that you want to
treat as “a whole”. It has to either happen in full, or not at all.
• Database transactions are logical units of work which must
all be performed to maintain data integrity

12. Transaction supports concurrency control..
 Many applications require a lot of users to access the data
simultaneously (e.g. airline booking systems)
 Uncontrolled simultaneous access can result in chaos, so some
controlling mechanism is required which provides by transaction.
It will probably be made up of smaller operations which
temporarily cause inconsistency

13. Need of Transaction...
E.g. Move money from one account to another.
T1. UPDATE tbl_accountA SET flt_balance = flt_balance – 100
WHERE int_accountNo = 123;
T2. UPDATE tbl_accountB SET flt_balance = flt_balance + 100
WHERE int_accountNo = 124;
Suppose system fails after Transaction T1, then amount 100
has been deducted from tbl_accountA but not credited in
tbl_accountB.

14. Peculiarities of Transactions
 No inconsistent state will arise.
 Transaction has only two states :
Either COMMIT (success) or ROLLBACK(fail) transaction. Which
means either complete the execution of statements(query) or leave if any error
occurs and undo all changes to begin-state.
 No data loss and no malicious data will arise.
 Assurance of data integrity.
 Manage recovery from system crashes.

15. Flow of a transaction
A transaction is the execution of a program that accesses the DB and
• starts with a BEGIN operation,
• followed by a sequence of READ and WRITE operations,
• ending with a COMMIT or ABORT operation.

16. ACID Properties of Transactions
ACID stands for:
• Atomicity
• Consistency
• Isolation
• Durability

17. Atomicity
- Each transaction be “all or nothing”.
- If one of transaction fails , the entire transaction fails.
- Including power failure, system crash.
- Committed transaction appears to be single(atomic).

18. Consistency
-Ensures that database remains consistent before the start of
transaction and after the transaction.
Isolation
-Each transaction is conserved i.e. , other operation can’t access
or see in an immediate state during a transaction.
-Each transaction is unaware of another transaction executing
concurrently in system.

19. Durability
-Once a transaction has done , it will persist, and not be undone.
-It survive system failure.
- It doesn’t imply permanent change , another transaction can
overwrite any change made by current transaction

20. Example: TRANSACTION IN STORED PROCEDURE.
[update bonus amount by 100 of employee whose age is greater than 50 and bonus>=1000]
DELIMITER //
CREATE PROCEDURE csp_chkAge()
BEGIN
DECLARE int_maxAge int; /* declare integer variable
int_maxAge */
START TRANSACTION; /*transaction starts here */
INSERT into tbl_status VALUES('Bonus set'); /*insert
‘Bonus set’ to tbl_status */
SELECT max(int_age) INTO int_maxAge FROM tbl_employee;
IF(int_maxAge>50) THEN
UPDATE tbl_employee SET int_bonus=int_bonus+100 WHERE
int_bonus>=1000; /*bonus increase by
1000 */
COMMIT;
ELSE
ROLLBACK; /* if age of employee less than 50 no change
will happen , transaction rollback, insertion in
tbl_status and updation in tbl_employee undo */

21. Pk_int_emp_id Vchr_emp_name Int_age Int_bonus
1 Johnson 35 900
2 Robert 28 850
3 Maxwell 55 1200
4 Steve 54 1100
tbl_employee
Pk_int_emp_id Vchr_emp_name Int_age Int_bonus
1 Johnson 35 900
2 Robert 28 850
3 Maxwell 55 1300
4 Steve 54 1200
after calling procedure csp_chkAge() and transaction commit
tbl_employee tbl_status
Vchr_status
Bonus set

22. Example: TRANSACTION WITH CURSOR
DELIMITER //
CREATE PROCEDURE csp_select()
BEGIN
DECLARE int_updtBonus int;
DECLARE bonus_cursor CURSOR FOR SELECT int_bonus
FROM tbl_employee where int_age >50 FOR UPDATE; /*declare
cursor for tbl_employee */
START TRANSACTION; /*transaction begins here
*/
OPEN bonus_cursor;
FETCH bonus_cursor INTO int_updtBonus; /*assign cursor
value to variable */
UPDATE tbl_employee SET int_bonus=int_bonus+100
WHERE int_updtBonus;
CLOSE bonus_cursor;
COMMIT;

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