Mysql SQL选择其他位置列的行为空的行
首先,如果标题令人困惑,请道歉。Mysql SQL选择其他位置列的行为空的行,mysql,sql,Mysql,Sql,首先,如果标题令人困惑,请道歉。 SQL不是我的强项,我在这方面已经工作了一段时间,我在mmoment的想法是加入,也许还有团队 Soto示例: record | type | key1 | key2 | data1 --------------------------------------- 1 | 1 | joe | smoe | 10 2 | 2 | homer | simpson | 20 3 | 1 | null |
SQL不是我的强项,我在这方面已经工作了一段时间,我在mmoment的想法是加入,也许还有团队 Soto示例:
record | type | key1 | key2 | data1
---------------------------------------
1 | 1 | joe | smoe | 10
2 | 2 | homer | simpson | 20
3 | 1 | null | null | 30
4 | 3 | bart | simpson | 40
其中主键由id、键1、键2组成
我只想要“type”行,其中key1不为null,key2不为null
因此,由于在记录3中,类型1有空键,因此我希望类型1的所有记录都不包括在派生表中。这里有一种相关的“不存在”方法:
select *
from T as t1
where not exists (
select *
from T as t2
where t2.type = t1.type and (t2.key1 is null or t2.key2 is null)
)
这里有一个使用非相关查询和分组的方法。也许这就是你的想法:
select *
from T as t1
where t1.type in (
select t2.type
from T as t2
group by t2.type
having count(*) = count(t2.key1) and count(*) = count(t2.key2)
)
因为我知道mysql查询计划可能对这些事情很敏感。下面是连接的等效项:
select t1.*
from T as t1
inner join
(
select t2.type
from T as t2
group by t2.type
having count(*) = count(t2.key1) and count(*) = count(t2.key2)
) as goodtypes
on goodtypes.type = t1.type
以下是一种相关的“不存在”方法:
select *
from T as t1
where not exists (
select *
from T as t2
where t2.type = t1.type and (t2.key1 is null or t2.key2 is null)
)
这里有一个使用非相关查询和分组的方法。也许这就是你的想法:
select *
from T as t1
where t1.type in (
select t2.type
from T as t2
group by t2.type
having count(*) = count(t2.key1) and count(*) = count(t2.key2)
)
因为我知道mysql查询计划可能对这些事情很敏感。下面是连接的等效项:
select t1.*
from T as t1
inner join
(
select t2.type
from T as t2
group by t2.type
having count(*) = count(t2.key1) and count(*) = count(t2.key2)
) as goodtypes
on goodtypes.type = t1.type
不需要漂亮的短语,也不需要缩写。我认为你的标题很好。不需要漂亮的词组,也不需要缩写。我认为你的头衔很好。