MYSQL练习随笔

案例1.子查询练习 

字段 说明
film_id 电影id
title 电影名称
description 电影描述信息
category_id 电影分类id
name 电影分类名称
last_update 电影分类最后更新时间
film_id 电影id
category_id 电影分类id
last_update 电影id和分类id对应关系的最后更新时间

CREATE TABLE IF NOT EXISTS film ( film_id smallint(5)  NOT NULL DEFAULT ‘0‘, title varchar(255) NOT NULL, description text, PRIMARY KEY (film_id));

CREATE TABLE category  ( category_id  tinyint(3)  NOT NULL , name  varchar(25) NOT NULL, `last_update` timestamp, PRIMARY KEY ( category_id ));

CREATE TABLE film_category  ( film_id  smallint(5)  NOT NULL, category_id  tinyint(3)  NOT NULL, `last_update` timestamp);

select title,description
from film 
where film_id in(select film_id from film_category 
             where category_id in(select category_id from category w
                                 where name=‘Action‘))    
#子查询解法
select f.title,f.description
from film as f inner join film_category as fc on f.film_id = fc.film_id
               inner join category as c on c.category_id = fc.category_id
where c.name = ‘Action‘;
#常规解法

名词解释补充

案例1：Explain解释

获取select * from employees对应的执行计划

explain select * from employees

MYSQL练习随笔

标签：更新   名称   使用   table   des   mys   plain   class   div