sql-server - Sql 查询协助。如何正确获取where子句中的项目

Question

我创建了这个简化的 sql 查询。它需要一个只有 2 个字符的级别代码（“GR”、“PH”...等），我需要更改查询以允许在一个实例中返回多个项目。

这是代码

    DECLARE @ALEVL_CODE varchar(5), @test varchar(100)
    SET @ALEVL_CODE = 'GR'
    SET @test = @ALEVL_CODE + ',' + 'PH'

-
                    select ALEVL_CODE  from PMP_Admissions_Letter_Data AD
                    INNER JOIN      PMP_LM_Review LMR
    ON              LMR.PMP_Letter_Data_ID = AD.PMP_Admissions_Letter_Data_ID
    WHERE           LMR.ToPrinter = 1 AND
                    LMR.Extracted = 0 AND 
                    AD.ALEVL_CODE = @ALEVL_CODE                 
                    AND
                    AD.DSCN_MAX_CODE = 'PA'

我遇到的问题是AD.ALEVL_CODE=@ALEVL_CODE where 子句中的行。我想成为类似 when @ALEVL_CODEis GRthen doGR和PHelse just do的东西@ALEVL_CODE。这有道理吗？一些帮助将不胜感激。

Answer 1

    AND (AD.ALEVL_CODE = @ALEVL_CODE
         OR (@ALEVL_CODE='GR' AND AD.ALEVL_CODE = 'PH'))

一个简化的替代方案。

Answer 2

            select ALEVL_CODE  from PMP_Admissions_Letter_Data AD
            INNER JOIN      PMP_LM_Review LMR
ON              LMR.PMP_Letter_Data_ID = AD.PMP_Admissions_Letter_Data_ID
WHERE           LMR.ToPrinter = 1 AND
            LMR.Extracted = 0 AND 
            ((@ALEVL_CODE = 'GR' AND AD.ALEVL_CODE in ('GR', 'PH')) 
                OR (@ALEVL_CODE <> 'GR' AND AD.ALEVL_CODE = @ALEVL_CODE))                 
            AND
            AD.DSCN_MAX_CODE = 'PA'

Answer 3

and case when (@ALEVL_CODE = 'GR') then AD.ALEVL_CODE in ('GR', 'PH') 
         else AD.ALEVL_CODE = @ALEVL_CODE
    end