MySQL View

MySQL View

In MySQL, View is a virtual table created by a query by joining one or more tables.

MySQL Create VIEW

A VIEW is created by SELECT statements. SELECT statements are used to take data from the source table to make a VIEW.

Syntax:

mysql> CREATE [OR REPLACE] VIEW view_name AS  
       SELECT columns  
       FROM tables  
       [WHERE conditions];  

Parameters:

OR REPLACE: It is optional. It is used when a VIEW already exist. If you do not specify this clause and the VIEW already exists, the CREATE VIEW statement will return an error.

view_name: It specifies the name of the VIEW that you want to create in MySQL.

WHERE conditions: It is also optional. It specifies the conditions that must be met for the records to be included in the VIEW.

The following example will create a VIEW name "trainer". This is a virtual table made by taking data from the table "courses".

mysql> CREATE VIEW trainer AS  
       SELECT course_name, course_trainer   
       FROM courses;  

mysql view

To see the created VIEW:

Syntax:

mysql view

MySQL Update VIEW

In MYSQL, the ALTER VIEW statement is used to modify or update the already created VIEW without dropping it.

Syntax:

mysql> ALTER VIEW view_name AS  
       SELECT columns  
       FROM table  
       WHERE conditions; 

Example:

The following example will alter the already created VIEW name "trainer" by adding a new column.

mysql> ALTER VIEW trainer AS  
       SELECT course_name, course_trainer, course_id  
       FROM courses;  

mysql view

To see the altered VIEW:

mysql> SELECT * FROM trainer; 

mysql view

MySQL Drop VIEW

You can drop the VIEW by using the DROP VIEW statement.

Syntax:

mysql> DROP VIEW [IF EXISTS] view_name;  

Parameters:

view_name: It specifies the name of the VIEW that you want to drop.

IF EXISTS: It is optional. If you do not specify this clause and the VIEW doesn't exist, the DROP VIEW statement will return an error.

Example:

mysql> DROP VIEW trainer; 

mysql view