Question

我正在尝试在CASE子句中编写WHERE语句，类似于此。我的问题是，最后我要说ELSE CalendarQuarter IN (@Q1,@Q2,@Q3,@Q4)。因此，如果没有满足这些条件，请执行其他操作。我无法弄清楚如何添加此ELSE语句。

AND CalendarQuarter in
(
    /*March, June, Sep 2010 Metcard*/
    (CASE WHEN DATEPART(yy,@year_end) = 2010 
        AND @ticketing_system = 'metcard' 
        AND DATEPART(mm,@year_end) IN (3,6,9)  THEN @Q1  END),
    (CASE WHEN DATEPART(yy,@year_end) = 2010
        AND @ticketing_system = 'metcard' 
        AND DATEPART(mm,@year_end) IN (3,6)  THEN @Q2  END),
    (CASE WHEN DATEPART(yy,@year_end) = 2010
        AND @ticketing_system = 'metcard' 
        AND DATEPART(mm,@year_end) IN (3)  THEN @Q3  END),

    /*March, June, Sep 2010 Metcard/Myki*/  
    (CASE WHEN DATEPART(yy,@year_end) = 2010 
        AND @ticketing_system = 'metcard/myki' 
        AND DATEPART(mm,@year_end) IN (9,6,3)  THEN @Q4  END),
    (CASE WHEN DATEPART(yy,@year_end) = 2010 
        AND @ticketing_system = 'metcard/myki' 
        AND DATEPART(mm,@year_end) IN (9,6)  THEN @Q3  END),
    (CASE WHEN DATEPART(yy,@year_end) = 2010 
        AND @ticketing_system = 'metcard/myki' 
        AND DATEPART(mm,@year_end) IN (9)  THEN @Q2  END),

    /*March, June, Sep 2013 Metcard/Myki*/
    (CASE WHEN DATEPART(yy,@year_end) = 2013 
        AND @ticketing_system = 'metcard/myki' 
        AND DATEPART(mm,@year_end) IN (3,6,9)  THEN @Q1  END),
    (CASE WHEN DATEPART(yy,@year_end) = 2013
        AND @ticketing_system = 'metcard/myki' 
        AND DATEPART(mm,@year_end) IN (3,6)  THEN @Q2  END),
    (CASE WHEN DATEPART(yy,@year_end) = 2013
        AND @ticketing_system = 'metcard/myki' 
        AND DATEPART(mm,@year_end) IN (3)  THEN @Q3  END),

    /*March, June, Sep 2013 Myki*/  
    (CASE WHEN DATEPART(yy,@year_end) = 2013 
        AND @ticketing_system = 'myki' 
        AND DATEPART(mm,@year_end) IN (9,6,3)  THEN @Q4  END),
    (CASE WHEN DATEPART(yy,@year_end) = 2013 
        AND @ticketing_system = 'myki' 
        AND DATEPART(mm,@year_end) IN (9,6)  THEN @Q3  END),
    (CASE WHEN DATEPART(yy,@year_end) = 2013 
        AND @ticketing_system = 'myki' 
        AND DATEPART(mm,@year_end) IN (9)  THEN @Q2  END),

    /*ELSE....IN (@Q1,@Q2,@Q3,@Q4)*/

)

Answer 1

我没有足够的声誉来为您的帖子添加评论，但听起来您想添加另一个案例陈述。 ELSE不应该有任何条件，它用于捕获与它附加的case语句中的任何条件不匹配的所有条件。

e.g。列foo可以包含1,2,3或4，我们希望将列分别设置为a，b，c或c。我们有以下案例陈述

CASE
    WHEN foo = 1
        THEN 'a'
    WHEN foo = 2
        THEN 'b'
    ELSE 'c'
END

我们不需要为3或4添加一个案例，因为它们与1或2不匹配，因此它们将由else处理，将它们设置为c。

如果您尝试向else语句添加另一个条件，则可以在else中使用另一个case语句。在这种情况下，我们希望将foo 3或4的值转换为x或y。

CASE
    WHEN foo = 1
        THEN 'a'
    WHEN foo = 2
        THEN 'b'
    ELSE CASE
            WHEN foo = 3
                THEN 'x'
            WHEN foo = 4
                THEN 'y'
            ELSE NULL
        END
END

当然，您可以使用您想要的任何值，您不需要在条件中评估单个列。

编辑：我使用你的case语句创建了一个例子。它在ELSE中有第二个case语句，允许你向else添加条件。

AND CalendarQuarter IN
                    (
                    CASE 
                        /*March, June, Sep 2010 Metcard*/
                        WHEN DATEPART(yy,@year_end) = 2010 
                                        AND @ticketing_system = 'metcard' 
                                        AND DATEPART(mm,@year_end) IN (3,6,9)  
                            THEN @Q1
                        WHEN DATEPART(yy,@year_end) = 2010
                                        AND @ticketing_system = 'metcard' 
                                        AND DATEPART(mm,@year_end) IN (3,6)  
                            THEN @Q2
                        WHEN DATEPART(yy,@year_end) = 2010
                                        AND @ticketing_system = 'metcard' 
                                        AND DATEPART(mm,@year_end) IN (3)  
                            THEN @Q3

                        /*March, June, Sep 2013 Metcard/Myki*/
                        CASE WHEN DATEPART(yy,@year_end) = 2010 
                                        AND @ticketing_system = 'metcard/myki' 
                                        AND DATEPART(mm,@year_end) IN (9,6,3)  
                            THEN @Q4
                        WHEN DATEPART(yy,@year_end) = 2010 
                                        AND @ticketing_system = 'metcard/myki' 
                                        AND DATEPART(mm,@year_end) IN (9,6)  
                            THEN @Q3
                        WHEN DATEPART(yy,@year_end) = 2010 
                                        AND @ticketing_system = 'metcard/myki' 
                                        AND DATEPART(mm,@year_end) IN (9)  
                            THEN @Q2

                        /*March, June, Sep 2013 Metcard/Myki*/
                        WHEN DATEPART(yy,@year_end) = 2013 
                                        AND @ticketing_system = 'metcard/myki' 
                                        AND DATEPART(mm,@year_end) IN (3,6,9)  
                            THEN @Q1
                        WHEN DATEPART(yy,@year_end) = 2013
                                        AND @ticketing_system = 'metcard/myki' 
                                        AND DATEPART(mm,@year_end) IN (3,6)  
                            THEN @Q2
                        WHEN DATEPART(yy,@year_end) = 2013
                                        AND @ticketing_system = 'metcard/myki' 
                                        AND DATEPART(mm,@year_end) IN (3)  
                            THEN @Q3

                        /*March, June, Sep 2013 Myki*/ 
                        WHEN DATEPART(yy,@year_end) = 2013 
                                        AND @ticketing_system = 'myki' 
                                        AND DATEPART(mm,@year_end) IN (9,6,3)  
                            THEN @Q4
                        WHEN DATEPART(yy,@year_end) = 2013 
                                        AND @ticketing_system = 'myki' 
                                        AND DATEPART(mm,@year_end) IN (9,6)  
                            THEN @Q3
                        WHEN DATEPART(yy,@year_end) = 2013 
                                        AND @ticketing_system = 'myki' 
                                        AND DATEPART(mm,@year_end) IN (9)  
                            THEN @Q2

                        ELSE CASE
                                WHEN [YOUR CONDITION HERE] IN (@Q1,@Q2,@Q3,@Q4)
                                    THEN [SOME RESULT]
                                END
                    END
                    )

上述声明将在条件满足后立即返回。另一种方法是使用原始case语句，但不使用else，而是使用上述条件的倒数。 e.g。

CASE 
    WHEN DATEPART(yy,@year_end) = 2013
        THEN CASE 
                WHEN @ticketing_system = 'myki' 
                    THEN CASE
                            WHEN DATEPART(mm,@year_end) NOT IN (9,6,3)
                                THEN (@Q1,@Q2,@Q3,@Q4)
                        END
                WHEN @ticketing_system = 'metcard/myki' 
                    THEN CASE
                            WHEN DATEPART(mm,@year_end) NOT IN (3,6,9)
                                THEN (@Q1,@Q2,@Q3,@Q4)
                        END
             END
    WHEN DATEPART(yy,@year_end) = 2010
        THEN CASE
                WHEN @ticketing_system = 'metcard/myki'
                    THEN CASE
                            WHEN DATEPART(mm,@year_end) NOT IN (9,6,3)
                                THEN (@Q1,@Q2,@Q3,@Q4)
                        END
                WHEN @ticketing_system = 'metcard' 
                    THEN CASE
                            WHEN DATEPART(mm,@year_end) NOT IN (3,6,9)
                                THEN (@Q1,@Q2,@Q3,@Q4)
                         END
            END
END

Answer 2

我建议你避免使用case条款并尝试使用：

WHERE (DATEPART(yy,@year_end) = 2010
AND @ticketing_system         = 'metcard'
AND DATEPART(mm,@year_end)   IN (3,6,9)
AND CalendarQuarter          IN (@Q1))
OR 
(DATEPART(yy,@year_end)    = 2010
AND @ticketing_system         = 'metcard'
AND DATEPART(mm,@year_end)   IN (3,6)
AND CalendarQuarter          IN (@Q2))
..................................
OR 
(DATEPART(yy,@year_end)    = 2013
AND @ticketing_system         = 'myki'
AND DATEPART(mm,@year_end)   IN (9)
AND CalendarQuarter          IN(@Q2) )
OR 
(CalendarQuarter          IN (@Q1,@Q2,@Q3,@Q4))

WHERE中使用ELSE的多个CASE

2 个答案: