Question

如何在传递参数时从查询中过滤记录，并在参数具有空值时返回all。

SELECT nfv.Company_id, COUNT(1) as NegativeFeedback,SUM(allocated_score) as ScoreSum
FROM dbo.NegativeFeedbackView nfv
WHERE ISNULL(nfv.comp_nature_id,0) = @compNatureId 
GROUP BY nfv.Company_id

Answer 1

使用IF/ELSE：

e.g。

IF @compNatureId IS NULL
BEGIN

    SELECT nfv.Company_id, COUNT(1) as NegativeFeedback,SUM(allocated_score) as ScoreSum
    FROM dbo.NegativeFeedbackView nfv
    WHERE ISNULL(nfv.comp_nature_id,0) = @compNatureId 
    GROUP BY nfv.Company_id

END
ELSE
BEGIN

    SELECT nfv.Company_id, COUNT(1) as NegativeFeedback,SUM(allocated_score) as ScoreSum
    FROM dbo.NegativeFeedbackView nfv
    GROUP BY nfv.Company_id

END

尝试将情境合并为一个查询：

SELECT nfv.Company_id, COUNT(1) as NegativeFeedback,SUM(allocated_score) as ScoreSum
FROM dbo.NegativeFeedbackView nfv
WHERE ISNULL(nfv.comp_nature_id,0) = @compNatureId 
OR @compNatureId IS NULL
GROUP BY nfv.Company_id

可能会产生次优计划，并且不能在comp_nature_id上使用任何索引（如果存在）。

Answer 2

下面是一个示例proc，它采用可选参数进行过滤。

CREATE PROCEDURE USP_MyProc(@FilterParameter AS VARCHAR(100) = NULL)

BEGIN

SELECT nfv.Company_id, COUNT(1) as NegativeFeedback,SUM(allocated_score) as ScoreSum
FROM dbo.NegativeFeedbackView nfv

WHERE
(@compNatureId  IS NULL OR ISNULL(nfv.comp_nature_id,0)= @compNatureId )

GROUP BY nfv.Company_id

END

传递参数时过滤a，不传递参数时返回all

2 个答案: