Oracle中如何使用基于Case语句的Group By？

Question

我有一个 SQL 查询，我使用 Oracle

CASE

来比较日期列是否小于或大于当前日期。但是我如何在

CASE

语句中使用

GROUP BY

语句呢？我想统计每种情况下的记录。

例如

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

但是尝试此操作时出现错误：

ORA-00904

。有什么建议吗？

Answer 1

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)

Answer 2

使用内联视图：

SELECT expired,
       count(*)
  FROM (SELECT (CASE
                   WHEN exp_date > SYSDATE THEN 1
                   WHEN exp_date <= SYSDATE THEN 2
                   ELSE 3
                 END) AS expired
          FROM mytable)
GROUP BY expired;

希望有帮助...

Answer 3

作为附加输入，虽然它与该线程无关，但您也可以聚合您的 case 语句，而无需在 group by 子句中提及它。

SELECT
   WORK_ORDER_NUMBER,
   SUM(CASE WHEN STOCK_CODE LIKE 'xxxx' THEN STOCK_QUANTITY ELSE 0 END) AS TOTAL
FROM Table
GROUP BY WORK_ORDER_NUMBER;

Answer 4

为什么不：

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