SQL Where 子句中的服务器条件

Question

我正在使用 SQL 服务器 class。我在使用存储过程中的条件 Where 子句时遇到问题。 3 个参数中的 2 个可以为 Null。

@Service nvarchar(50),
@Country nvarchar(50)  = NULL,
@Region nvarchar(50) = NULL

as 

SELECT
  CASE @Service
    WHEN 'Army' THEN Sum(Army)
    WHEN 'Navy' THEN Sum(Navy)
    When 'Marine_Corps' then Sum(Marine_Corps)
    When 'Air_Force' then Sum(Air_Force)
                ELSE NULL
  END

  as "ServiceTotal"

FROM
  All_Records

 WHERE 

if @Country is not null @Country and if @Region !=Null @Region = Region

如何重组 Where 子句？我来自 Access 背景。

GetTotals Navy

OR

GetTotals Navy,Albania,Europe

我想将服务设置为必填项，将国家和地区设置为可选项。所以我希望能够像这样调用程序。所以，如果我不指定地区和国家，它应该只是 return all Navy。

这可能吗？

Answer 1

就性能而言，最好不要在 WHERE 子句中使用函数。

SELECT  CASE @Service
            WHEN 'Army' THEN Sum(Army)
            WHEN 'Navy' THEN Sum(Navy)
            When 'Marine_Corps' then Sum(Marine_Corps)
            When 'Air_Force' then Sum(Air_Force)
            ELSE NULL
        END AS "ServiceTotal"
FROM All_Records
WHERE Country = CASE WHEN @Country IS NOT NULL THEN @Country ELSE Country END
AND Region = CASE WHEN @Region IS NOT NULL THEN @Region ELSE Region END

使用ISNULL函数

SELECT  CASE @Service
            WHEN 'Army' THEN Sum(Army)
            WHEN 'Navy' THEN Sum(Navy)
            When 'Marine_Corps' then Sum(Marine_Corps)
            When 'Air_Force' then Sum(Air_Force)
            ELSE NULL
        END AS "ServiceTotal"
FROM All_Records
WHERE Country = ISNULL(@Country ,Country)
AND Region = ISNULL(@Region ,Country)

Answer 2

试试这个：

Where (@country is null or @country = country)
And (@region is null or @region = region)

您要搜索的内容称为包罗万象的查询。

SQL Where 子句中的服务器条件

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stored-procedures