从三列中获取最新日期

Question

ID     Date1           Date2            Date3   
158    5/3/13 15:11    2/20/13 11:38    2/20/13 11:38

我想从这三列中获取最新日期.

Answer 1

SELECT CASE WHEN Date1 IS NOT NULL 
             AND Date1>=COALESCE(Date2,CAST('0001-01-01 00:00' AS DATETIME2)) 
             AND Date1>=COALESCE(Date3,CAST('0001-01-01 00:00' AS DATETIME2)) THEN Date1 
            WHEN Date2 IS NOT NULL 
             AND Date2>=COALESCE(Date1,CAST('0001-01-01 00:00' AS DATETIME2))
             AND Date2>=COALESCE(Date3,CAST('0001-01-01 00:00' AS DATETIME2)) THEN Date2 
            WHEN Date3 IS NOT NULL 
             AND Date3>=COALESCE(Date1,CAST('0001-01-01 00:00' AS DATETIME2))
             AND Date3>=COALESCE(Date2,CAST('0001-01-01 00:00' AS DATETIME2)) THEN Date3 
       END AS latest
FROM t1

例子