选择DISTINCT多列

Question

我在检索DISTINCT记录时遇到问题。场景如下：现在我的查询是

Select a,b,c from TABLE_NAME
(COMPLEX_INNER JOIN LOGIC)

我想要前两列值应该唯一的记录。我知道可以做到

GROUP BY 

条款。因此查询将变为

Select a,b,c from TABLE_NAME
(COMPLEX_INNER JOIN LOGIC)
GROUP BY a,b

但由于c并没有出现在SQL服务器的聚合函数或组中，所以出现了以下错误：

选择列表中的列"c"无效，因为它既不包含在聚合函数中，也不包含在GROUP BY子句中

Answer 1

您可以将查询放入CTE中，并使用row_number（）函数来确定要获取哪些行
类似这样的东西：

with C as
(
  Select a,b,c,
         row_number() over(partition by a, b order by SomeColumn) as rn
  from TABLE_NAME
  --(COMPLEX_INNER JOIN LOGIC)
)
select a, b, c
from C
where rn = 1

工作样品：

declare @T table
(
  a int,
  b int,
  c int
)
insert into @T values
(1, 1, 1),
(1, 1, 2),
(2, 2, 1),
(2, 2, 2)
;with C as
(
  select a, b, c,
         row_number() over(partition by a, b order by c) as rn
  from @T         
)
select a, b, c
from C
where rn = 1

结果：

a           b           c
----------- ----------- -----------
1           1           1
2           2           1

Answer 2

像这样使用

select c,q.a,q.b from TABLE_NAME inner join 
(
Select a,b from TABLE_NAME
(COMPLEX_INNER JOIN LOGIC)
GROUP BY a,b) q 
on q.a=TABLE_NAME.a