MySQL view

One 、 Create view

grammar ：

create view View name

as

Query statement ;

USE myemployees;

The advantages of view ：

When creating a multi table query statement , It's easy to have a lot of duplicate code , Creating views can effectively avoid duplicate code , It's very convenient to use .

1. The query name contains a The employee name of the character 、 Department name and job information

① establish

CREATE VIEW myv1

AS

SELECT last_name,department_name,job_title

FROM employees e

JOIN departments d ON e.department_id = d.department_id

JOIN jobs j ON j.job_id = e.job_id;

​

② Use

SELECT * FROM myv1 WHERE last_name LIKE '%a%';

Two 、 View modification

create or replace view View name

as

Query statement ;

3、 ... and 、 Delete view

​

grammar ：drop view View name , View name ,…;

​

DROP VIEW emp_v1,emp_v2,myv3;

​

Four 、 View view

DESC myv3;

SHOW CREATE VIEW myv3;

5、 ... and 、 Update of view

CREATE OR REPLACE VIEW myv1

AS

SELECT last_name,email,salary*12*(1+IFNULL(commission_pct,0)) "annual salary"

FROM employees;

​

CREATE OR REPLACE VIEW myv1

AS

SELECT last_name,email

FROM employees;

1. Insert

INSERT INTO myv1 VALUES(' Xiaohong ','[email protected].com')

2. modify

UPDATE myv1 SET last_name = ' Xiao Ming ' WHERE last_name=' Xiaohong ';

3. Delete

DELETE FROM myv1 WHERE last_name = ' Xiao Ming ';

The view should try not to modify the data in the table, because it changes the data of several tables , So don't change it. It's usually used for querying and omitting duplicate code