从嵌套的Select T-SQL中选择

I wish to modify data by selecting them in a inner query and count one of them modified.. It gives error..

我希望通过在内部查询中选择数据并计算其中一个数据被修改。它给错误. .

select count(cvs) from
(
  select 
  cvs,
  (case Citycode when 123 then 'test' else 'other' end) as CityName ,
  (case ProductCode when '000' then 'test3' when 'ss' then 'xtr' else 'ddd' end) as CardName
  from Applications
)

4 个解决方案

#1

you need to give an alias to the subquery:

您需要为子查询提供别名:

select count(x.cvs) from
(
  select 
  cvs,
  (case Citycode when 123 then 'test' else 'other' end) as CityName ,
  (case ProductCode when '000' then 'test3' when 'ss' then 'xtr' else 'ddd' end) as CardName
  from Applications
) x

#2

Why not just do this instead?

为什么不这样做呢?

SELECT COUNT(cvs)
    FROM Applications

#3

It appears your query could be simplified to..

看来您的查询可以简化为。

SELECT COUNT(cvs) FROM Applications

Is there a reason you have the select nested and you are ignoring the other columns being selected?

有什么原因使您具有选择嵌套，而忽略了正在选择的其他列?

#4

Two things I see off the bat:

我立刻看到了两件事:

1 - You don't need the nested subquery for what you are doing in the example. You could just as easily do:

1 -在本例中，您不需要嵌套子查询。你也可以很容易地做到:

SELECT COUNT(cvs) FROM application

从应用程序选择计数(cvs)

2 - You need an alias for the subquery, like (<subquery>) as SubQ

2 -你需要一个子查询的别名，例如( )作为SubQ。

#1