SQL练习29:使用join查询方式找出没有分类的电影id以及名称
题目链接:牛客网
题目描述
使用join
查询方式找出没有分类的电影id
以及名称。
film表
字段 | 说明 |
---|---|
film_id | 电影id |
title | 电影名称 |
description | 电影描述信息 |
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 |
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 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);
输入数据为:
INSERT INTO film VALUES(1,'ACADEMY DINOSAUR','A Epic Drama of a Feminist And a Mad Scientist who must Battle a Teacher in The Canadian Rockies');
INSERT INTO film VALUES(2,'ACE GOLDFINGER','A Astounding Epistle of a Database Administrator And a Explorer who must Find a Car in Ancient China');
INSERT INTO film VALUES(3,'ADAPTATION HOLES','A Astounding Reflection of a Lumberjack And a Car who must Sink a Lumberjack in A Baloon Factory');
INSERT INTO category VALUES(1,'Action','2006-02-14 20:46:27');
INSERT INTO category VALUES(2,'Animation','2006-02-14 20:46:27');
INSERT INTO category VALUES(3,'Children','2006-02-14 20:46:27');
INSERT INTO category VALUES(4,'Classics','2006-02-14 20:46:27');
INSERT INTO category VALUES(5,'Comedy','2006-02-14 20:46:27');
INSERT INTO category VALUES(6,'Documentary','2006-02-14 20:46:27');
INSERT INTO category VALUES(7,'Drama','2006-02-14 20:46:27');
INSERT INTO category VALUES(8,'Family','2006-02-14 20:46:27');
INSERT INTO category VALUES(9,'Foreign','2006-02-14 20:46:27');
INSERT INTO category VALUES(10,'Games','2006-02-14 20:46:27');
INSERT INTO category VALUES(11,'Horror','2006-02-14 20:46:27');
INSERT INTO film_category VALUES(1,6,'2006-02-14 21:07:09');
INSERT INTO film_category VALUES(2,11,'2006-02-14 21:07:09');
输出为:
电影id | 名称 |
---|---|
3 | ADAPTATION HOLES |
解法一
按照题目的要求使用LEFT JOIN
来将film
表和film_category
表连接起来,选择last_update IS NULL
的数据。
SELECT f.film_id, title
FROM film f LEFT JOIN film_category fc
ON f.film_id = fc.film_id
WHERE last_update IS NULL
解法二
不使用JOIN
,使用子查询的方式,查询film_category
表中的film_id
列,再在film
表中查询film_id
不再子查询结果列中的数据。
SELECT film_id, title
FROM film
WHERE film_id NOT IN (SELECT film_id
FROM film_category)