SQL练习题(2)-牛客网

牛客网在线编程网址：https://www.nowcoder.com/activity/oj

(默认使用SQLite)

 

film表

字段	说明
film_id	电影id
title	电影名称
description	电影描述信息

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));

category表

字段	说明
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

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

film_category表

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

 

题目1：

查找描述信息中包括robot的电影对应的分类名称以及电影数目，而且还需要该分类对应电影数量>=5部（指的是所有电影中该分类的电影数量>=5）

with category_num as(
    select category_id, count(*) num from film_category
    GROUP BY category_id having num >= 5
) 
select category.name, count(*)
FROM category, film_category
WHERE category.category_id = film_category.category_id
AND film_category.category_id IN (select category_id from category_num)
AND film_id IN
(
    select film_id from film Where description LIKE '%robot%'
)
GROUP BY name;

或者

select category.name, count(*)
FROM category, film_category,
(
    select category_id, count(*) num from film_category
    GROUP BY category_id having num >= 5
) as category_num
WHERE category.category_id = film_category.category_id
AND film_category.category_id = category_num.category_id
AND film_id IN
(
    select film_id from film Where description LIKE '%robot%'
)
GROUP BY name;

 

 

题目2：

使用join查询方式找出没有分类的电影id以及名称

select film_id, title FROM
(
    select film.film_id, film.title, film_category.category_id
    FROM film LEFT JOIN film_category
    ON film.film_id = film_category.film_id
) table_join
WHERE category_id IS NULL;

 

题目3：

使用子查询的方式找出属于Action分类的所有电影对应的title,description

select title, description from film
WHERE film_id IN
(
    select film_id FROM
    category INNER JOIN film_category
    ON category.category_id = film_category.category_id
    AND category.name = 'Action'
);

或

select title, description
FROM film, film_category
WHERE film.film_id = film_category.film_id
AND film_category.category_id IN (select category_id from category where name = 'Action');