傳遞非空參數在SQL Server中返回NULL記錄

Question

我最近發佈了一個關於如何處理SQL Server Reporting Services中的NULL值的問題。問題位於Handle NULL values in SQL Server Reporting Services。

應用WHERE @MyParam=MyCol OR @MyParam IS NULL會面臨一個問題，即如果我選擇單個非空值（從下拉列表中並將其作爲SQL Server傳遞），這也會帶來NULL值記錄。它應該只帶來Non NULL值的記錄。

如果選擇非空記錄，應該如何避免空記錄？

Answer 1

你所尋找的是一個異或（XOR）：

-- Exclusive OR is an either/or combination which, 
-- using => as "is defined as" symbol, can be shown as: 
-- 
-- x XOR y => (x AND (NOT y)) OR ((NOT x) AND y) 

-- x => @MyParam = MyCol 
-- y => @MyParam IS NULL 



-- DECLARE @MyParam NVARCHAR(32) = 'MC1,MC2'; -- returns two lines 
-- DECLARE @MyParam NVARCHAR(32) = 'MC1';  -- returns one line 
    DECLARE @MyParam NVARCHAR(32) = NULL;  -- returns one line 


DECLARE @MyParamXML XML = N'<root><r>' + replace(@MyParam,',','</r><r>') + '</r></root>' 

;WITH SOExample AS 
(
    SELECT cast('MC1' AS NVARCHAR(12)) AS MyCol, 'Line 1' AS MyCol2 UNION ALL 
    SELECT  'MC2'       , 'Line 2'    UNION ALL 
    SELECT  NULL       , 'Line NULL' 
) 
SELECT * from SOExample 
WHERE 
     (@MyParam IS NULL  AND ISNULL(MyCol,'<NULL Value>') = '<NULL Value>') 
    OR (@MyParam IS NOT NULL AND 
     SOExample.MyCol IN 
      (SELECT SSRSlist.MyParams.value('.','NVARCHAR(32)') as MyParam 
      FROM @MyParamXML.nodes('//root/r') as SSRSlist(MyParams)))