MySQL函数FIND_IN_SET介绍

背景

前几天面试遇见一个问题，如果一个表字段对应另一个表多个字段，问怎么用一条SQL语句实现，因为没有接触过FIND_IN_SET，当时想了其他很多办法都没有有效解决，后来发现可以使用FIND_IN_SET函数实现。

准备工作

mysql> create table movie (
    -> id int primary key auto_increment,
    -> name varchar(20),
    -> type varchar(20)
    -> );
Query OK, 0 rows affected (0.05 sec)

mysql> create table movie_type( 
    > id int primary key auto_increment, 
    > type_name varchar(20), 
    > type_desc varchar(255)
    > );
Query OK, 0 rows affected (0.04 sec)

mysql> insert into movie values (null, '速度与激情','1,3,6');
Query OK, 1 row affected (0.03 sec)

mysql> insert into movie values (null, '万物生长','2,3,5');
Query OK, 1 row affected (0.00 sec)

mysql> insert into movie values (null, '战狼','1,3');
Query OK, 1 row affected (0.02 sec)

mysql> insert into movie values (null, '星际迷航','10');
Query OK, 1 row affected (0.03 sec)

mysql> insert into movie_type values(1,'动作','动作大片'),(2,'爱情','爱情片'),(3,'惊悚','惊悚片'),(4,'伦理','伦理片'),(5,'科幻','科幻片');
Query OK, 5 rows affected (0.03 sec)
Records: 5  Duplicates: 0  Warnings: 0

试用FIND_IN_SET函数

mysql> select FIND_IN_SET('2','5,4,3,2,1');
+------------------------------+
| FIND_IN_SET('2','5,4,3,2,1') |
+------------------------------+
|                            4 |
+------------------------------+
1 row in set (0.00 sec)

mysql> select * from movie where FIND_IN_SET(2,type);
+----+--------------+-------+
| id | name         | type  |
+----+--------------+-------+
|  2 | 万物生长     | 2,3,5 |
+----+--------------+-------+
1 row in set (0.00 sec)

mysql> select a.name,a.type, group_concat(b.type_name),
          group_concat(b.type_desc order by b.id desc SEPARATOR ' # ') as type_desc
       from movie a 
       inner join movie_type b 
       on FIND_IN_SET(b.id,a.type)    
       group by a.id ;
+-----------------+-------+---------------------------+-----------------------------------+
| name            | type  | group_concat(b.type_name) | type_desc                         |
+-----------------+-------+---------------------------+-----------------------------------+
| 速度与激情      | 1,3,6 | 动作,惊悚                 | 惊悚片 # 动作大片                 |
| 万物生长        | 2,3,5 | 惊悚,爱情,科幻            | 科幻片 # 惊悚片 # 爱情片          |
| 战狼            | 1,3   | 动作,惊悚                 | 惊悚片 # 动作大片                 |
+-----------------+-------+---------------------------+-----------------------------------+
3 rows in set (0.00 sec)

当时想的正则匹配不能实现
mysql> select a.name,a.type, group_concat(b.type_name),
          group_concat(b.type_desc order by b.id desc SEPARATOR ' # ') as type_desc
       from movie a 
       inner join movie_type b 
       on a.type REGEXP b.id    
       group by a.id ;
+-----------------+-------+---------------------------+-----------------------------------+
| name            | type  | group_concat(b.type_name) | type_desc                         |
+-----------------+-------+---------------------------+-----------------------------------+
| 速度与激情      | 1,3,6 | 动作,惊悚                 | 惊悚片 # 动作大片                 |
| 万物生长        | 2,3,5 | 惊悚,爱情,科幻            | 科幻片 # 惊悚片 # 爱情片          |
| 战狼            | 1,3   | 动作,惊悚                 | 惊悚片 # 动作大片                 |
| 星际迷航        | 10    | 动作                      | 动作大片                          |
+-----------------+-------+---------------------------+-----------------------------------+
4 rows in set (0.00 sec)

可以看到正则匹配查询匹配出的数据并不正确，顺便复习了一下group_concat的使用方式。

整理自网络

Svoid

2015-04-24

来自 “ ITPUB博客 ” ，链接：http://blog.itpub.net/29733787/viewspace-1604394/，如需转载，请注明出处，否则将追究法律责任。

转载于:http://blog.itpub.net/29733787/viewspace-1604394/