假设现在有三张这样的表，如何合并成一张表，急求！？

[Bleachswh]

表一：first
id grade
1 20
2 19
表二：second
id grade
1 18
3 19
表三：third
id grade
1 20
4 17

我想合并成表四:sum
id grade
1 58
2 19
3 19
4 17

有什么办法吗？sql语句不精通，求助……

[ACMAIN_CHM]

select id,sum(grade)
from(
	select id      ,grade from first
	union all
	select id      ,grade from second
	union all
	select id      ,grade from third
	union all
) t
group by id

[ACMAIN_CHM]

Bleachswh 结帖率：0%

引用

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