从嵌套选择T-SQL中选择

我希望通过在内部查询中选择它们来修改数据
并计算其中一个修改..
它给出错误..

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
)

解决方法

您需要为子查询提供一个别名：

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