如何根据Oracle中的Case语句使用Group By？ [英] How do I use Group By based on a Case statement in Oracle?

问题描述

我有一个使用Oracle CASE 的SQL查询来比较日期列是小于还是大于当前日期。但是，如何在 GROUP BY -statement中使用 CASE -statement？我想在每种情况下计数记录。

I have an SQL-query where I use Oracle CASE to compare if a date column is less than or greater than current date. But how do I use that CASE-statement in a GROUP BY-statement? I would like to count the records in each case.

例如

E.g.

select
    (case
        when exp_date > sysdate then 1
        when exp_date <= sysdate then 2
        else 3
     end) expired, count(*)
from mytable
group by expired

但我在尝试此操作时遇到错误： ORA-00904 。任何建议？

But I get an error when trying this: ORA-00904. Any suggestions?

推荐答案

select
(case
    when exp_date > sysdate then 1
    when exp_date <= sysdate then 2
    else 3
 end) expired, count(*)
from mytable
group by (case
    when exp_date > sysdate then 1
    when exp_date <= sysdate then 2
    else 3
 end)

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