关于mysql:聊聊mysql的单列多值存储

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本文次要钻研一下 mysql 如何用一个列来存储多个值

实例

用 bit 类型

  • 建表及数据筹备 

    -- 这里定义了 bit(3)，示意有 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 值也能够，比方 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              |
+---------------+------------------+

  • 位运算查问 

    -- 查问第二位有值的数据
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              |
+---------------+------------------+

-- 查问第三位有值的数据
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              |
+---------------+------------------+

-- 查问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

  • 建表及数据筹备 

    create table t_bigint_demo(
 id int NOT NULL AUTO_INCREMENT PRIMARY KEY,
 multi_value bigint not null default 0
);

-- 假如这里定义了 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           |
+-------------+

  • 查问 

    -- 查问蕴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              |
+-------------+------------------+

-- 查问蕴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              |
+-------------+------------------+

-- 查问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

  • 建表及数据筹备 

    create table t_varchar_demo(
 id int NOT NULL AUTO_INCREMENT PRIMARY KEY,
 multi_value varchar(255) not null default ''
);

-- 假如这里定义了 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       |
+-------------+

  • 查问 

    -- 查问蕴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       |
+-------------+

-- 查问蕴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       |
+-------------+

-- 查问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

  • 建表及数据筹备 

    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');

  • 查问 

    -- 查问蕴含第二个枚举的数据，能够用位运算也能够用 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       |
+-------------+

-- 查问蕴含第三个枚举的数据，能够用位运算也能够用 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       |
+-------------+

-- 查问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解决，具体能够用 bit、int/bigint、varchar、set 类型来实现，毛病是不反对索引。

doc

  • bit-type
  • bit-functions
  • function_find-in-set
  • set
正文完
mysql
发表至： mysql
2022-04-03
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