Question

我在下面有查询，

SELECT CASE 
        WHEN floor(months_between(CAL_DATE, BIRTH_DATE) / 12) BETWEEN 0
                AND 20
            THEN '1'
        WHEN floor(months_between(CAL_DATE, BIRTH_DATE) / 12) BETWEEN 21
                AND 30
            THEN '2'
        WHEN floor(months_between(CAL_DATE, BIRTH_DATE) / 12) BETWEEN 31
                AND 40
            THEN '3'
        WHEN floor(months_between(CAL_DATE, BIRTH_DATE) / 12) BETWEEN 41
                AND 50
            THEN '4'
        ELSE '5'
        END ) Age_Band
FROM dual

有没有办法为表达式floor(months_between(CAL_DATE, BIRTH_DATE) / 12)提供别名，并在下面的case语句中使用它。

CASE floor(months_between(CAL_DATE, BIRTH_DATE) / 12) **age**
        WHEN **age**  BETWEEN 0 AND 20  THEN '1'

Answer 1

你不能为CASE语句添加别名，但是，为了使事情更具可读性和紧凑性，我使用子查询进行计算。

#AAA

Answer 2

您可以使用CTE或子查询。这是一个CTE，因为其他人有一个子查询：

WITH floor AS
(
   SELECT floor(months_between(CAL_DATE, BIRTH_DATE) / 12) AS floor
   FROM dual
)
SELECT CASE 
    WHEN f.floor BETWEEN 0 AND 20 THEN '1'
    WHEN f.floor BETWEEN 21 AND 30 THEN '2'
    WHEN f.floor BETWEEN 31 AND 40 THEN '3'
    WHEN f.floor BETWEEN 41 AND 50 THEN '4'
    ELSE '5' END AS Age_Band
FROM floor f

Answer 3

仅当您使用子查询时：

SELECT CASE 
    WHEN z.flor BETWEEN 0 AND 20 THEN '1'
    WHEN z.flor BETWEEN 21 AND 30 THEN '2'
    WHEN z.flor BETWEEN 31 AND 40 THEN '3'
    WHEN z.flor BETWEEN 41 AND 50 THEN '4'
    else '5' end Age_Band
FROM (SELECT floor(months_between
       (CAL_DATE, BIRTH_DATE) / 12) flor
      From dual)z

但你也可以这样做：

 Select case when months_between(CAL_DATE, BIRTH_DATE) > 60 then 5 
         else 1 + floor(months_between(CAL_DATE, BIRTH_DATE) / 240) end
 From dual

不会做同样的事情吗？

为CASE语句中使用的表达式赋予别名的任何方法

3 个答案: