Question

我有以下声明：

SELECT
    CASE 
       WHEN account_id IS NOT NULL 
          THEN value 
          ELSE value_2 
    END AS result

如何在选择陈述中使用'结果'？

SELECT
    CASE 
       WHEN account_id IS NOT NULL 
          THEN value 
          ELSE value_2 
    END AS result,
    result as result_2

此代码不起作用

Answer 1

您无法在定义它的同一级别使用列别名。您必须使用派生表：

select result, 
       result as result_2, 
       ... other columns ...
from (
  select CASE WHEN account_id IS NOT NULL THEN value ELSE value_2 END AS result, 
         .... other columns ...
  from ...
  where ...
) t

其中re

PostgreSQL中SELECT中的CASE语句

1 个答案: