mysql的单列多值存储实例详解

序

本文主要研究一下mysql如何用一个列来存储多个值

实例

用bit类型

• 建表及数据准备

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-- 这里定义了bit(3)，表示有3位，第一位1，第二位2，第三位4 create table t_bit_demo(     id int NOT NULL AUTO_INCREMENT PRIMARY KEY ,     multi_value bit (3) not null default 0 );   -- 这里插入了1，2，4的组合值 insert into t_bit_demo(multi_value) values (b '000' ); insert into t_bit_demo(multi_value) values (b '001' ); insert into t_bit_demo(multi_value) values (b '010' ); insert into t_bit_demo(multi_value) values (b '011' ); insert into t_bit_demo(multi_value) values (b '100' ); insert into t_bit_demo(multi_value) values (b '101' ); insert into t_bit_demo(multi_value) values (b '110' ); insert into t_bit_demo(multi_value) values (b '111' );   -- 这里直接插入int值也可以，比如5相当于101 -- insert into t_bit_demo(multi_value) values(5);   SELECT multi_value+0, BIN(multi_value) FROM t_bit_demo; + ---------------+------------------+ | multi_value+0 | BIN(multi_value) | + ---------------+------------------+ | 0             | 0                | | 1             | 1                | | 2             | 10               | | 3             | 11               | | 4             | 100              | | 5             | 101              | | 6             | 110              | | 7             | 111              | + ---------------+------------------+

• 位运算查询

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-- 查询第二位有值的数据 select multi_value+0,BIN(multi_value) from t_bit_demo where multi_value & 2 + ---------------+------------------+ | multi_value+0 | BIN(multi_value) | + ---------------+------------------+ | 2             | 10               | | 3             | 11               | | 6             | 110              | | 7             | 111              | + ---------------+------------------+   -- 查询第三位有值的数据 select multi_value+0,BIN(multi_value) from t_bit_demo where multi_value & 4 + ---------------+------------------+ | multi_value+0 | BIN(multi_value) | + ---------------+------------------+ | 4             | 100              | | 5             | 101              | | 6             | 110              | | 7             | 111              | + ---------------+------------------+   -- 查询只有第三位有值的数据 select multi_value+0,BIN(multi_value) from t_bit_demo where multi_value = 4 select multi_value+0,BIN(multi_value) from t_bit_demo where multi_value = 4 + ---------------+------------------+ | multi_value+0 | BIN(multi_value) | + ---------------+------------------+ | 4             | 100              | + ---------------+------------------+

• 更新

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select id ,multi_value + 0 , BIN (multi_value) from t_bit_demo + - - - - + - - - - - - - - - - - - - - - + - - - - - - - - - - - - - - - - - - + | id | multi_value + 0 | BIN (multi_value) | + - - - - + - - - - - - - - - - - - - - - + - - - - - - - - - - - - - - - - - - + | 1  | 0             | 0                | | 2  | 1             | 1                | | 3  | 2             | 10               | | 4  | 3             | 11               | | 5  | 4             | 100              | | 6  | 5             | 101              | | 7  | 6             | 110              | | 8  | 7             | 111              | + - - - - + - - - - - - - - - - - - - - - + - - - - - - - - - - - - - - - - - - +   - - 将 id 为 7 的值移除第二个枚举 update t_bit_demo set multi_value = b '100' where id = 7 select id ,multi_value + 0 , BIN (multi_value) from t_bit_demo where id = 7 + - - - - + - - - - - - - - - - - - - - - + - - - - - - - - - - - - - - - - - - + | id | multi_value + 0 | BIN (multi_value) | + - - - - + - - - - - - - - - - - - - - - + - - - - - - - - - - - - - - - - - - + | 7  | 4             | 100              | + - - - - + - - - - - - - - - - - - - - - + - - - - - - - - - - - - - - - - - - +

用int/bigint类型

• 建表及数据准备

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create table t_bigint_demo(     id int NOT NULL AUTO_INCREMENT PRIMARY KEY ,     multi_value bigint not null default 0 );   -- 假设这里定义了1，2，4三个枚举值 insert into t_bigint_demo(multi_value) values (0); insert into t_bigint_demo(multi_value) values (1); insert into t_bigint_demo(multi_value) values (2); insert into t_bigint_demo(multi_value) values (3); insert into t_bigint_demo(multi_value) values (4); insert into t_bigint_demo(multi_value) values (5); insert into t_bigint_demo(multi_value) values (6); insert into t_bigint_demo(multi_value) values (7);   select multi_value from t_bigint_demo + -------------+ | multi_value | + -------------+ | 0           | | 1           | | 2           | | 3           | | 4           | | 5           | | 6           | | 7           | + -------------+

• 查询

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-- 查询包含第二个枚举的数据 select multi_value,BIN(multi_value) from t_bigint_demo where multi_value & 2 + -------------+------------------+ | multi_value | BIN(multi_value) | + -------------+------------------+ | 2           | 10               | | 3           | 11               | | 6           | 110              | | 7           | 111              | + -------------+------------------+   -- 查询包含第三个枚举的数据 select multi_value,BIN(multi_value) from t_bigint_demo where multi_value & 4 + -------------+------------------+ | multi_value | BIN(multi_value) | + -------------+------------------+ | 4           | 100              | | 5           | 101              | | 6           | 110              | | 7           | 111              | + -------------+------------------+   -- 查询值为第三个枚举的数据 select multi_value,BIN(multi_value) from t_bigint_demo where multi_value =4 + -------------+------------------+ | multi_value | BIN(multi_value) | + -------------+------------------+ | 4           | 100              | + -------------+------------------+

• 更新

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select id,multi_value,BIN(multi_value) from t_bigint_demo + ----+-------------+------------------+ | id | multi_value | BIN(multi_value) | + ----+-------------+------------------+ | 1  | 0           | 0                | | 2  | 1           | 1                | | 3  | 2           | 10               | | 4  | 3           | 11               | | 5  | 4           | 100              | | 6  | 5           | 101              | | 7  | 6           | 110              | | 8  | 7           | 111              | + ----+-------------+------------------+   -- 将id为7的值移除第二个枚举 update t_bigint_demo set multi_value = b '100' where id=7 select id,multi_value,BIN(multi_value) from t_bigint_demo where id=7 + ----+-------------+------------------+ | id | multi_value | BIN(multi_value) | + ----+-------------+------------------+ | 7  | 4           | 100              | + ----+-------------+------------------+

用varchar类型

• 建表及数据准备

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create table t_varchar_demo(     id int NOT NULL AUTO_INCREMENT PRIMARY KEY ,     multi_value varchar (255) not null default '' );   -- 假设这里定义了1，2，4三个枚举值 insert into t_varchar_demo(multi_value) values ( '1' ); insert into t_varchar_demo(multi_value) values ( '2' ); insert into t_varchar_demo(multi_value) values ( '1,2' ); insert into t_varchar_demo(multi_value) values ( '4' ); insert into t_varchar_demo(multi_value) values ( '1,4' ); insert into t_varchar_demo(multi_value) values ( '2,4' ); insert into t_varchar_demo(multi_value) values ( '1,2,4' );   select multi_value from t_varchar_demo + -------------+ | multi_value | + -------------+ | 1           | | 2           | | 1,2         | | 4           | | 1,4         | | 2,4         | | 1,2,4       | + -------------+

• 查询

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-- 查询包含第二个枚举的数据 select multi_value from t_varchar_demo where find_in_set( '2' ,multi_value) + -------------+ | multi_value | + -------------+ | 2           | | 1,2         | | 2,4         | | 1,2,4       | + -------------+   -- 查询包含第三个枚举的数据 select multi_value from t_varchar_demo where find_in_set( '4' ,multi_value) + -------------+ | multi_value | + -------------+ | 4           | | 1,4         | | 2,4         | | 1,2,4       | + -------------+   -- 查询只有第三个枚举的数据 select multi_value from t_varchar_demo where multi_value = '4' + -------------+ | multi_value | + -------------+ | 4           | + -------------+

• 更新

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select * from t_varchar_demo + ----+-------------+ | id | multi_value | + ----+-------------+ | 1  | 1           | | 2  | 2           | | 3  | 1,2         | | 4  | 4           | | 5  | 1,4         | | 6  | 2,4         | | 7  | 1,2,4       | + ----+-------------+   -- 将id为7的值移除第二个枚举 update t_varchar_demo set multi_value = '1,4' where id=7 select * from t_varchar_demo where id=7 + ----+-------------+ | id | multi_value | + ----+-------------+ | 7  | 1,4         | + ----+-------------+

用set类型

• 建表及数据准备

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create table t_set_demo(     id int NOT NULL AUTO_INCREMENT PRIMARY KEY ,     multi_value set ( '1' , '2' , '4' ) not null default '' );   insert into t_set_demo(multi_value) values ( '' ); insert into t_set_demo(multi_value) values ( '1' ); insert into t_set_demo(multi_value) values ( '2' ); insert into t_set_demo(multi_value) values ( '1,2' ); insert into t_set_demo(multi_value) values ( '4' ); insert into t_set_demo(multi_value) values ( '1,4' ); insert into t_set_demo(multi_value) values ( '2,4' ); insert into t_set_demo(multi_value) values ( '1,2,4' );

• 查询

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-- 查询包含第二个枚举的数据，可以用位运算也可以用find_in_set select multi_value from t_set_demo where multi_value&2 select multi_value from t_set_demo where find_in_set( '2' ,multi_value) + -------------+ | multi_value | + -------------+ | 2           | | 1,2         | | 2,4         | | 1,2,4       | + -------------+   -- 查询包含第三个枚举的数据，可以用位运算也可以用find_in_set select multi_value from t_set_demo where multi_value&4 select multi_value from t_set_demo where find_in_set( '4' ,multi_value) + -------------+ | multi_value | + -------------+ | 4           | | 1,4         | | 2,4         | | 1,2,4       | + -------------+   -- 查询值为第三个枚举的数据 select multi_value from t_set_demo where multi_value= '4' + -------------+ | multi_value | + -------------+ | 4           | + -------------+

• 更新

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select * from t_set_demo + ----+-------------+ | id | multi_value | + ----+-------------+ | 1  |             | | 2  | 1           | | 3  | 2           | | 4  | 1,2         | | 5  | 4           | | 6  | 1,4         | | 7  | 2,4         | | 8  | 1,2,4       | + ----+-------------+   -- 将id为7的值移除第二个枚举 update t_set_demo set multi_value = '1,4' where id=7 select * from t_set_demo where id=7 select * from t_set_demo where id=7 + ----+-------------+ | id | multi_value | + ----+-------------+ | 7  | 1,4         | + ----+-------------+

小结

mysql用单列存储多值通常用于一对多的反范式处理，具体可以用bit、int/bigint、varchar、set类型来实现，缺点是不支持索引。

doc

• bit-type
• bit-functions
• function_find-in-set
• set

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原文链接：https://juejin.cn/post/7082207515789754404