在SQL Server中执行嵌套case语句逻辑的最佳方法

SELECT
    col1,
    col2,
    col3,
        WHEN condition 
                WHEN condition1 
                        WHEN condition2
                        THEN calculation1
                        ELSE calculation2
                        WHEN condition2
                        THEN calculation3
                        ELSE calculation4
                WHEN condition1 
                        WHEN condition2 
                        THEN calculation5
                        ELSE calculation6
                        WHEN condition2 
                        THEN calculation7
                        ELSE calculation8
    END AS 'calculatedcol1',
    col4,
    col5 -- etc
FROM table

SELECT
    col1,
    col2,
    col3,
    CASE WHEN condition THEN
      CASE WHEN condition1 THEN
        CASE WHEN condition2 THEN calculation1
        ELSE calculation2 END
        CASE WHEN condition2 THEN calculation3
        ELSE calculation4 END
    ELSE CASE WHEN condition1 THEN 
      CASE WHEN condition2 THEN calculation5
      ELSE calculation6 END
    ELSE CASE WHEN condition2 THEN calculation7
         ELSE calculation8 END
    END AS 'calculatedcol1',
    col4,
    col5 -- etc
FROM table

select  datediff(dd,Invdate,'2009/01/31')+1 as DaysOld, 
    case when datediff(dd,Invdate,'2009/01/31')+1 >150 then 6 else
        case when datediff(dd,Invdate,'2009/01/31')+1 >120 then 5 else 
            case when datediff(dd,Invdate,'2009/01/31')+1 >90 then 4 else 
                case when datediff(dd,Invdate,'2009/01/31')+1 >60 then 3 else 
                    case when datediff(dd,Invdate,'2009/01/31')+1 >30 then 2 else 
                        case when datediff(dd,Invdate,'2009/01/31')+1 >30 then 1 end 
    end as Bucket
from rm20090131atb

SELECT
    col1,
    col2,
    col3,
        WHEN condition1 THEN calculation1 
        WHEN condition2 THEN calculation2
        WHEN condition3 THEN calculation3
        WHEN condition4 THEN calculation4
        WHEN condition5 THEN calculation5
        ELSE NULL         
    END AS 'calculatedcol1',
    col4,
    col5 -- etc
FROM table

CASE WHEN condition1 = true AND condition2 = true THEN calculation1 
     WHEN condition1 = true AND condition2 = false 
     ELSE 'what so ever' END,

CASE WHEN a = 1 AND b = 1 AND c = 1 THEN '1'
     WHEN a = 0 AND b = 0 AND c = 1 THEN '0'
ELSE '0' END,

    SELECT
    col1,
    col2,
    col3,
        WHEN condition1 THEN calculation1 
        WHEN condition2 THEN calculation2
        WHEN condition3 THEN calculation3

在SQL Server中执行嵌套case语句逻辑的最佳方法

8 个回答