从结果查询中选择count(*) [英] Select count(*) from result query

问题描述

我需要您的帮助，这是我的SQL查询:

I need help from you, this is my sql query:

select count(SID) 
from Test 
where Date = '2012-12-10' 
group by SID

这是我的结果:

|2|
|3|
|4|
|3|

现在我必须计算第一个查询的结果！

and now I have to count the results from first query!

Expected result: 4 

推荐答案

您可以将查询包装在另一个SELECT中:

You can wrap your query in another SELECT:

select count(*)
from
(
  select count(SID) tot  -- add alias
  from Test 
  where Date = '2012-12-10' 
  group by SID
) src;  -- add alias

请参见带有演示的SQL小提琴

为使其正常工作，count(SID)需要一个列别名，并且您必须为子查询本身提供一个别名.

In order for it to work, the count(SID) need a column alias and you have to provide an alias to the subquery itself.

这篇关于从结果查询中选择count(*)的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！