在嵌套SELECT中比较Count from Outer SELECT？

Question

我有这个SQL查询，

select * from (select * from .......) as a
where 1 = case when CountOfInnerSelect = 1 Then 1 ELSE ............

我可以在外部SELECT中获得内部选择的计数吗？

Answer 1

是的：

select * from (select count(0) as cnt from .......) as a
where 1 = case when a.cnt = 1 Then 1 ELSE ............

Answer 2

您的WHERE Clause没有多大意义，因为它像过滤器一样应用于此处。 （即;类似于WHERE myCount = 1）

SELECT * FROM
(SELECT c1,c2,c3,..,Cn,COUNT(*) AS myCount
 FROM YourTable
 GROUP BY c1,c2,c3,..,Cn
) A
WHERE 1 = CASE myCount WHEN 1 THEN 1 ELSE... END