sql - 如何在sql中重用子查询？

Question

我有如下查询

select columns
from (select columns1
      from result_set
      where condition_common and condition1) as subset1
      join
      (select columns2
       from result_set
       where condition_common and condition2) as subset2 
      on subset1.somekey = subset2.somekey

我想以某种方式重用

select columns
from result_set
where condition_common

我把上面的查询过分简化了，但实际上上面的选择是庞大而复杂的。我不想承担确保两者同步的负担

我没有任何以编程方式重用它的方法。排除了 T-SQL。我只能写简单的查询。这是应用程序限制。

有没有办法在单个语句中重用相同的子查询

Answer 1

如果您使用的是 SQL Server 2005+，请使用公用表表达式(CTE)：

with cte as (
      select columns
      from result_set
      where condition_common
    )
select columns
from cte  as subset1
      join
      cte as subset2 
         on subset1.somekey = subset2.somekey
where otherconditions