从结果查询中选择count(*)

本文介绍了从结果查询中选择count(*)的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 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.