MySQL views allow users to create virtual tables based on the result set of SELECT statements. Views can reference tables but have restrictions like not allowing subqueries or system variables. The CREATE VIEW statement is used to define a view with an AS clause specifying the SELECT statement. Views offer benefits like easier maintenance and security but can impact performance.

1. MySQL Views
Reggie Niccolo Santos
UP ITDC

2. Outline

What is a view?

Restrictions when using views

Syntax

Sample CREATE VIEW statement

Advantages and disadvantages of using
views

3. What is a view?

Virtual table based on the result-set of an
SQL statement

The fields in a view are fields from one or
more real tables in the database

4. Restrictions on views

The SELECT statement cannot contain a
subquery

The SELECT statement cannot refer to
system or user variables

Any table or view referred to in the
definition must exist

5. Restrictions on views

A temporary VIEW cannot be created

A VIEW cannot be associated with a trigger

6. Syntax: CREATE VIEW
CREATE
[OR REPLACE]
[ALGORITHM = {UNDEFINED | MERGE |
TEMPTABLE}]
[DEFINER = { user | CURRENT_USER }]
[SQL SECURITY { DEFINER | INVOKER }]
VIEW view_name [(column_list)]
AS select_statement
[WITH [CASCADED | LOCAL] CHECK OPTION]

7. Example: View
CREATE OR REPLACE VIEW `view_track_details`
AS
SELECT TRK.id, TRK.title AS 'track_title',
TRK.rating, TRK.len AS 'length',
TRK.count AS 'play_count', ALB.title AS
'album_title', ART.`name` AS 'artist',
GNR.`name` AS 'genre'
FROM track TRK
JOIN album ALB ON TRK.album_id = ALB.id
JOIN artist ART ON ALB.artist_id = ART.id
JOIN genre GNR ON TRK.genre_id = GNR.id;

8. “Avie w is no thing m o re than a pse udo -table do ing
the wo rk o f a de fine d q ue ry. ”

9. Advantages and disadvantages
Advantages:

Easily maintainable pseudo-tables of data

Added level of security by not exposing the
table structure of the application
Disadvantages:

Performance hit

10. Advantages and disadvantages
Advantages:

Easily maintainable pseudo-tables of data

Added level of security by not exposing the
table structure of the application
Disadvantages:

Performance hit

11. References

http://www.w3schools.com/sql/sql_view.asp

Http://net.tutsplus.com/tutorials/databases/introdu

Http://zetcode.com/databases/mysqltutorial/views