MySQL-将表转换为其他表 [英] MySQL - turn table into different table
问题描述
此刻我可能看不到很清楚的内容,但是我在MySQL中有一个表,如下所示:
I'm probably not seeing things very clear at this moment, but I have a table in MySQL which looks like this:
ID | a | b | c
1 | a1 | b1 | c1
2 | a2 | b2 | c2
由于某种原因(实际上是在另一个表上的联接-基于ID
,但是我认为如果有人可以帮助我完成这一部分,我自己可以自己做剩下的事情),则我需要这些行像这样:
For some reason (actually a join on another table - based on ID
, but I think if someone can help me out with this part, I can do the rest myself), I needed those rows to be like this instead:
1 | a1 | a
1 | b1 | b
1 | c1 | c
2 | a2 | a
2 | b2 | b
2 | c2 | c
因此,基本上,我需要查看以下行:ID
,columntitle
,value
有什么办法可以轻松做到这一点?
So basically, I need to view the rows like: ID
, columntitle
, value
Is there any way to do this easily?
推荐答案
您正尝试取消透视. MySQL没有unpivot函数,因此您必须使用UNION ALL
查询将列转换为行:
You are trying to unpivot the data. MySQL does not have an unpivot function, so you will have to use a UNION ALL
query to convert the columns into rows:
select id, 'a' col, a value
from yourtable
union all
select id, 'b' col, b value
from yourtable
union all
select id, 'c' col, c value
from yourtable
请参见带有演示的SQL小提琴.
这也可以使用CROSS JOIN
来完成:
select t.id,
c.col,
case c.col
when 'a' then a
when 'b' then b
when 'c' then c
end as data
from yourtable t
cross join
(
select 'a' as col
union all select 'b'
union all select 'c'
) c
请参见带有演示的SQL小提琴
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