Question

我遇到了以下从COGNOS生成的代码：

  CASE 
    WHEN CASE 
            WHEN 'FIELD1' LIKE 'VAL1'
                THEN 1
            WHEN 'FIELD1' LIKE 'VAL2'
                THEN 2
            WHEN 'FIELD1' LIKE 'VAL3'
                THEN 3
            ELSE 4
            END = 1
        THEN 'M'
    WHEN CASE 
            WHEN 'FIELD1' LIKE 'VAL1'
                THEN 1
            WHEN 'FIELD1' LIKE 'VAL2'
                THEN 2
            WHEN 'FIELD1' LIKE 'VAL3'
                THEN 3
            ELSE 4
            END = 2
        THEN 'Q'
    WHEN CASE 
            WHEN 'FIELD1' LIKE 'VAL1'
                THEN 1
            WHEN 'FIELD1' LIKE 'VAL2'
                THEN 2
            WHEN 'FIELD1' LIKE 'VAL3'
                THEN 3
            ELSE 4
            END = 3
        THEN 'Y'
    ELSE 'T'
    END AS 'VAL4'

我无法确定＆＃39; =＆＃39;的重要性。运营商跟随＆＃39; END = nn＆＃39;。此外，CASE块似乎是重复的，不提供区别值。

Answer 1

这可能更清楚

 CASE 
   WHEN (
     CASE 
        WHEN 'FIELD1' LIKE 'VAL1' THEN 1
        WHEN 'FIELD1' LIKE 'VAL2' THEN 2
        WHEN 'FIELD1' LIKE 'VAL3' THEN 3
        ELSE 4
     END
   ) = 1 THEN 'M'

   WHEN (
     CASE 
       WHEN 'FIELD1' LIKE 'VAL1' THEN 1
       WHEN 'FIELD1' LIKE 'VAL2' THEN 2
       WHEN 'FIELD1' LIKE 'VAL3' THEN 3
       ELSE 4
     END 
   ) = 2 THEN 'Q'

   WHEN (
     CASE 
       WHEN 'FIELD1' LIKE 'VAL1' THEN 1
       WHEN 'FIELD1' LIKE 'VAL2' THEN 2
       WHEN 'FIELD1' LIKE 'VAL3' THEN 3
       ELSE 4
     END
   ) = 3 THEN 'Y'
   ELSE 'T'
 END AS 'VAL4'

基本上外壳的每一个＆＃39;当＆＃39;选项，另一案例陈述

所以，

如果Field1是＆＃39; VAL1＆＃39;然后结果将是＆＃39; M＆＃39;
如果Field1是＆＃39; VAL2＆＃39;然后结果将是Q＆＃39; Q＆＃39;
如果Field1是＆＃39; VAL3＆＃39;那么结果将是＆＃39; Y＆＃39;

如果Field1是其他任何东西，那将是＆＃39; T＆＃39;

Answer 2

比@ SpaceUser7448更简化，这看起来像：

SELECT 
CASE 
    WHEN 'FIELD1' LIKE 'VAL1' THEN 'M'
    WHEN 'FIELD1' LIKE 'VAL2' THEN 'Q'
    WHEN 'FIELD1' LIKE 'VAL3' THEN 'Y'
    ELSE 'T'
END AS 'VAL4'

TSQL CASE SYNTAX END = nn

2 个答案: