mysql的单列多值存储实例详解

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


 	-- 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


 	-- 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


 	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


 	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


 	-- 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


 	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


 	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


 	-- 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


 	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


 	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


 	-- 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


 	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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