sql learning

1. MySQL Lectures Notes
Stored Procedures,Triggers, Program
Access
Dr Lisa Ball
2008

2. Sources
1. dev.mysql.com
2. www.mysqltutorial.org
3. www.digitalpropulsion.org
4. www.databasedesign-resource.com/
mysql-triggers.html

3. Trigger Example
DELIMITER $$ -- set delimeter (allow ; inside)
CREATE TRIGGER newsCounter
AFTER INSERT ON News
FOR EACH ROW BEGIN
INSERT INTO NewsCount (newsItemCount)
(SELECT count(*) FROM News);
END;
$$
DELIMITER ; -- reset delimeter

4. Sample DB
CREATE TABLE NewsCategories
( catID int not null auto_increment,
catName varchar(32),
primary key(catID));
CREATE TABLE News
( newsID int not null auto_increment,
catID int not null,
title varchar(32) not null, txt blob,
primary key(newsID));
CREATE TABLE NewsCount
( newsItemCount int );

5. Trigger Example
DELIMITER $$
CREATE TRIGGER newsCategoryHandler
AFTER DELETE ON NewsCategories
FOR EACH ROW BEGIN
DELETE FROM News
WHERE catID=OLD.catID;
END;
$$
DELIMETER ;
-- Note: can reference NEW.attr on insert, update

6. Trigger Example
DELIMITER $$
CREATE TRIGGER newsCounter
AFTER INSERT ON News
FOR EACH ROW BEGIN
DELETE FROM NewsCount;
INSERT INTO NewsCount (newsItemCount)
(SELECT count(*) FROM News);
END;
$$

7. Trigger Statements
 DROP TRIGGER newsCounter;
 SHOW TRIGGERS;
 One trigger per event, per table
 Can add procedural elements, such as IF
statements
 See reference 4 (databasedesign-resource)
for another example

8. Stored Procedures
 Why go to the trouble of extracting logic from your application, putting it into a
different format, and placing it on the database server? There are several
advantages to doing so. Here is a (incomplete) list of some of the most commonly
sited advantages:
 MySQL stored procedures can greatly cut down on the amount of traffic going back
and forth over your network. (usually FASTER in general than using app program)
 Stored procedures can greatly improve the security of your database server. SQL
that is executed on the server is not subject to SQL injection attacks.
 Stored procedures provide a way to abstract and separate data access routines
from the business logic of your application.
 Stored procedures allow these routines to be accessed by programs using different
platforms and API's, and make your applications more portable.
 From source 4 (databasedesign-resource)

9. Stored Procedures
 Block structured language similar to Oracle
PL/SQL and IBM DB2 SQL
 Some folks recommend using MySQL query
browser to aid creation, but can be done from
command line
 Seeing what you have
• SHOW PROCEDURE STATUS;
• SHOW PROCEUDRE LIKE ‘%Test%’;
• SHOW CREATE PROCEDURE myproc;

10. Stored Procedures
 Sample DB
-- create News table, be sure to be in a 'test' DB
CREATE TABLE News
(NewsID int auto_increment not null,
Title varchar(32),
primary key(NewsID))

11. Stored Procedures
DELIMITER $$
DROP PROCEDURE IF EXISTS sprocTest $$
CREATE PROCEDURE sprocTest (id int, title varchar(32))
BEGIN
-- INSERT NEW RECORD IF PREEXISTING RECORD DOESNT EXIST
IF (id = 0) THEN
SET id = null;
END IF;
IF (id IS NOT NULL) AND (EXISTS
(SELECT * FROM News WHERE NewsID=id))
THEN
UPDATE News SET Title=title WHERE NewsID=id;
ELSE
INSERT INTO News (Title) VALUES (title);
END IF;
END $$
DELIMITER ;
To call:
CALL sprocTest(1,'Some News Title'); -- this will update recordID 1

12. Stored Procedures
 Using cursors
• Let’s us loop on each row returned from a query
(the result set)
• see design-resources link (also on next slide)

13. stored procedure using
cursors in a loop
To use:
call events(‘11/09’);
more detailed tutorial
at mysqltutorial.org

14. Program DB Access
 First:
• Chapter 9 Slides 18-37 from Elmasri 5th edition
 Some sources for Java access
• http://www.kitebird.com/articles/jdbc.html
• http://www.cs.ucdavis.edu/~devanbu/teaching/160/docs/mys
ql_java.pdf
• http://www.romow.com/computer-blog/how-to-use-mysql-with-java
/
 Can also access mysql with Perl, PHP, Python, Ruby