TSQL-CASE-WHEN语句的多个别名

我有一个查询，它从满足条件的表中选择列，问题是这个逻辑重复了好几次（对于所需的每一列，重复一次），并且想知道是否有更好的方法

SELECT
  CASE 
    WHEN (date1 IS NULL) THEN [date2]       
    WHEN (date1 IS NOT NULL OR ( date1 IS NOT NULL AND date2 IS NOT NULL )) THEN [date1]
    ELSE ''
  END AS selectedDate

//Repeat above statement for [day], [hour], [minute]

我想知道是否有可能将这些case语句聚合到具有单独别名的同一语句下，因为它们都依赖于相同的条件，而不是为每列多次重写同一语句，例如，我尝试了以下方法：

SELECT
  CASE 
    WHEN (date1 IS NULL) THEN [date2] as "selectedDate", [day2] as "day", [hour2] as "hour", [minute2] as "minute"  
    WHEN (date1 IS NOT NULL OR ( date1 IS NOT NULL AND date2 IS NOT NULL )) THEN [date1] as "selectedDate", [day1] as "day", [hour1] as "hour", [minute1] as "minute"   
    ELSE ''

---

不是以你描述的方式

另一种选择是使用或：

---

否。每列都需要自己的select语句

对于这个CASE语句的特定应用，可以使用

---

您可以编写一个函数来保存CASE逻辑，只要向它提供日期就行了。@Jens我是这么想的，但我必须将列作为参数传递，而不是值传递，不是吗？

select 
    SelectedDate = coalesce(date1,date2)
  , [Day]        = coalesce(day1,day2)
  , [Hour]       = coalesce(hour1,hour2)
  , [Minute]     = coalesce(minute1,minute2)
from t

SELECT COALESCE(date1, date2) AS selectedDate FROM SomeTable