sql - 在 SQL Server 2008 中使用嵌套 CASE 语句

Question

我的逻辑一定有点古怪，因为当我测试以确保这些 CASE 语句为真时，我不会得到预期的结果......

例如，如果 Sample1 = 'FI'、Sample2 = 'GOVT' 和 Sample3 = 'GOVT'，我不明白'OKFI' ...我知道我一定有一些古怪的逻辑...

对这些事情的最佳实践有什么想法吗？

CREATE FUNCTION SampleFunction
(
    @Sample1 varchar(50),
  @Sample2 varchar(50) = null,
  @Sample3 varchar(50) = null
)
RETURNS VARCHAR(255)
AS
BEGIN

declare @output varchar(255)



SET @output = 

CASE WHEN @Sample1 = 'CASH' THEN 'CASH' 

WHEN @Sample1 = 'ST' THEN 
    CASE WHEN @Sample2 ='TBILL' THEN
        CASE WHEN @Sample3 = 'TBILL' THEN 'OKFI' 

WHEN @Sample1 = 'FI' THEN
    CASE WHEN @Sample2 = 'GOVT' THEN
        CASE WHEN @Sample3 = 'GOVT' THEN 'OKFI'

WHEN @Sample1 = 'DERV' THEN
    CASE WHEN @Sample2 = 'CURRCONT' THEN 
        CASE WHEN @Sample3 = 'FORWARD' THEN 'CASH'
            WHEN @Sample3 = 'SPOT' THEN 'CASH' 
WHEN @Sample2 = 'SWAP' THEN
    CASE WHEN @Sample3 = 'CURRSWAP' THEN 'CASH'
        WHEN @Sample3 = 'INDXSWAP' THEN 'OTHER'

WHEN @Sample2 = 'FUTURE' THEN
CASE WHEN @Sample3 = 'COMFUT' THEN 'COM'
    WHEN @Sample3 = 'BFUT' THEN 'OKFI'
    WHEN @Sample3 = 'NDXFUT' THEN 'OKSHARES' 
    WHEN @Sample3 = 'EQFUT' THEN 'OKSHARES' 
    WHEN @Sample3 = 'CURRFUT' THEN 'CASH'

WHEN @Sample2 = 'OPTION' THEN
CASE WHEN @Sample3 = 'CUROPTION' THEN 'CASH' END

ELSE 'OTHER' 

END END END
END END END
END END END RETURN @Output

END -- FUNCTION

Answer 1

您应该创建@table 变量，甚至是包含列 Sample1、Sample2、Sample3、Output 的物理永久表 - 在其中插入所有组合和所需的输出，然后只需选择 Output 基于您的 @Sample1、@Sample2、@Sample3 变量。

这样在 CASE 中有几十个 CASE，你只会迷路。

类似这样的:

CREATE FUNCTION SampleFunction2
    (
      @Sample1 VARCHAR(50) ,
      @Sample2 VARCHAR(50) = NULL ,
      @Sample3 VARCHAR(50) = NULL
    )
RETURNS VARCHAR(255)
AS 
    BEGIN

        DECLARE @output VARCHAR(255)


        DECLARE @tempResults TABLE
            (
              Sample1 VARCHAR(50) ,
              Sample2 VARCHAR(50) ,
              Sample3 VARCHAR(50) ,
              [Output] VARCHAR(255)
            )

        INSERT  INTO @tempResults
        VALUES   ( 'CASH', NULL, NULL, 'CASH' )         
                ,( 'ST', 'TBILL', 'TBILL', 'OKFI' )
                ,( 'FI', 'GOVT', 'GOVT', 'OKFI' )
                ,( 'DERV', 'CURRCONT', 'FORWARD', 'CASH' )
                ,( 'DERV', 'CURRCONT', 'SPOT', 'CASH' )
                ,( NULL, 'SWAP', 'CURRSWAP', 'CASH' )
                ,( NULL, 'SWAP', 'INDXSWAP', 'OTHER' )
                ,( NULL, 'FUTURE', 'COMFUT', 'COM' )
                ,( NULL, 'FUTURE', 'BFUT', 'OKFI' )
                ,( NULL, 'FUTURE', 'NDXFUT', 'OKSHARES' )
                ,( NULL, 'FUTURE', 'EQFUT', 'OKSHARES' )
                ,( NULL, 'FUTURE', 'CURRFUT', 'CASH' )
                ,( NULL, 'OPTION', 'CUROPTION', 'CASH' )


        SELECT  @output = [Output]
        FROM    @tempResults
        WHERE   (@Sample1 IS NULL OR Sample1 = @Sample1)
            AND (@Sample2 IS NULL OR Sample2 = @Sample2)
            AND (@Sample3 IS NULL OR Sample3 = @Sample3)

        IF @output IS NULL SET @output = 'OTHER' 

        RETURN @output
    END

SQLFiddle DEMO

如果您想坚持使用 CASE，则原始查询的问题是放错了 ENDs :

CREATE FUNCTION SampleFunction
(
    @Sample1 varchar(50),
  @Sample2 varchar(50) = null,
  @Sample3 varchar(50) = null
)
RETURNS VARCHAR(255)
AS
BEGIN

declare @output varchar(255)



SET @output = 

CASE WHEN @Sample1 = 'CASH' THEN 'CASH' 

    WHEN @Sample1 = 'ST' THEN 
        CASE WHEN @Sample2 ='TBILL' THEN
            CASE WHEN @Sample3 = 'TBILL' THEN 'OKFI' 
            END
        END      

    WHEN @Sample1 = 'FI' THEN
        CASE WHEN @Sample2 = 'GOVT' THEN
            CASE WHEN @Sample3 = 'GOVT' THEN 'OKFI'
            END
        END

    WHEN @Sample1 = 'DERV' THEN
        CASE WHEN @Sample2 = 'CURRCONT' THEN 
            CASE WHEN @Sample3 = 'FORWARD' THEN 'CASH'
                WHEN @Sample3 = 'SPOT' THEN 'CASH' 
            END
        END      

    WHEN @Sample2 = 'SWAP' THEN
        CASE WHEN @Sample3 = 'CURRSWAP' THEN 'CASH'
            WHEN @Sample3 = 'INDXSWAP' THEN 'OTHER'
        END

    WHEN @Sample2 = 'FUTURE' THEN
        CASE WHEN @Sample3 = 'COMFUT' THEN 'COM'
            WHEN @Sample3 = 'BFUT' THEN 'OKFI'
            WHEN @Sample3 = 'NDXFUT' THEN 'OKSHARES' 
            WHEN @Sample3 = 'EQFUT' THEN 'OKSHARES' 
            WHEN @Sample3 = 'CURRFUT' THEN 'CASH'
        END

    WHEN @Sample2 = 'OPTION' THEN
        CASE WHEN @Sample3 = 'CUROPTION' THEN 'CASH' 
        END

    ELSE 'OTHER' 


  END RETURN @Output

END -- FUNCTION

SQLFiddle DEMO