Question

我有一个不是由我编写的存储过程。你能帮我翻译一下CASE条款中的WHERE陈述吗？

   --Declaring the parameter for SP
DECLARE
        @CompanyGuids varchar(8000) = '29634AF7-D0A2-473D-9574-405C23E10F02'
--Declaring table variable that will contain only CompanyGuid 
DECLARE @CompanyGuidsTbl TABLE(Guid uniqueidentifier)
    IF @CompanyGuids IS NULL
    BEGIN
        INSERT INTO @CompanyGuidsTbl
        SELECT DISTINCT CompanyGuid FROM  tblCompanies 
    END
    ELSE
    BEGIN
        INSERT INTO @CompanyGuidsTbl
        SELECT * FROM dbo.StringOfGuidsToTable(@CompanyGuids,',')
    END
--Select statement
SELECT Col1,
       Col2,
       Col3
FROM    MyTable1 INNER JOIN MyTable2
 /*  this is where I am confused  */
WHERE   
        CASE WHEN @CompanyGuids IS NOT NULL
        THEN   
        CASE WHEN tblCompanies.CompanyGuid in (SELECT Guid FROM @CompanyGuidsTbl)
            THEN 1 ELSE 0 END
        ELSE 1
        END = 1

如果我错了，请纠正我：

  "So if the parameter @CompanyGuids is NOT NULL, then we are checking if table @CompanyGuidsTbl has assigned parameter and if it does - then we gonna use it, but if it does not - ??? "

也许有办法重写它？感谢

Answer 1

一个构造不良的声明肯定，但是它是最终检查真值声明，其中1 = 1.首先检查一个空变量，然后如果变量不为空它检查tblCompanies中的CompanyGUID是否在提供的列表中在变量中，如果找到则返回1（因此1 = 1为真，因此记录匹配），或者如果未找到（在这种情况下0 = 1，这是假的，因此记录不匹配）。可怕的东西！

如何在WHERE子句中转换嵌套的CASE语句

1 个答案: