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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
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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 | +---------------+------------------+
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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 | +---------------+------------------+
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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
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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 | +-------------+
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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 | +-------------+------------------+
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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
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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 | +-------------+
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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 | +-------------+
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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
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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');
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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 | +-------------+
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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