存儲過程為參數NULL時的處理方法

准備一些數據：

 

SET ANSI_NULLS ON
GO

SET QUOTED_IDENTIFIER ON
GO

CREATE TABLE [dbo].[Goods](
    [Projname] [nvarchar](10) NULL,
    [version] [nvarchar](10) NULL,
    [state] [nvarchar](3) NULL
) ON [PRIMARY]
GO


INSERT INTO  [dbo].[Goods] ([Projname],[version],[state])
VALUES
(N'A項目',N'啟動會版',N'已審核'),
(N'A項目',N'方案版',N'已審核'),
(N'A項目',N'施工圖版',N'未審核'),
(N'B項目',N'    啟動會版',N'未審核'),
(N'B項目',N'    方案版',N'未審核'),
(N'B項目',N'    施工圖版',N'未審核')

GO

 

先來看看下面2句SQL語句，參數有值和NULL所查詢到的結果：

 

DECLARE @Projname NVARCHAR(10) = N'A項目'
SELECT [Projname],[version],[state] FROM [dbo].[Goods] WHERE [Projname] = @Projname
GO


DECLARE @Projname NVARCHAR(10) = NULL
SELECT [Projname],[version],[state] FROM [dbo].[Goods] WHERE [Projname] = @Projname
GO

 

方法一：

 

DECLARE @Projname NVARCHAR(10) = N'A項目'
SELECT [Projname],[version],[state] FROM [dbo].[Goods] WHERE [Projname] = @Projname
GO


DECLARE @Projname NVARCHAR(10) = NULL
SELECT [Projname],[version],[state] FROM [dbo].[Goods] WHERE [Projname] =
CASE WHEN @Projname IS NULL THEN [Projname] ELSE @Projname END

GO

 

方法二：

 

DECLARE @Projname NVARCHAR(10) = N'A項目'
SELECT [Projname],[version],[state] FROM [dbo].[Goods] WHERE [Projname] = @Projname
GO


DECLARE @Projname NVARCHAR(10) = NULL
SELECT [Projname],[version],[state] FROM [dbo].[Goods] WHERE [Projname] = @Projname
 OR @Projname IS NULL
GO

 

方法三：

 

DECLARE @Projname NVARCHAR(10) = N'A項目'
SELECT [Projname],[version],[state] FROM [dbo].[Goods] WHERE [Projname] = @Projname
GO


DECLARE @Projname NVARCHAR(10) = NULL
SELECT [Projname],[version],[state] FROM [dbo].[Goods] WHERE [Projname] = 
IIF(ISNULL(@Projname, N'') = N'', [Projname], @Projname)
GO

 

方法四：

 

DECLARE @Projname NVARCHAR(10) = N'A項目'
SELECT [Projname],[version],[state] FROM [dbo].[Goods] WHERE [Projname] = @Projname
GO


DECLARE @Projname NVARCHAR(10) = NULL
SELECT [Projname],[version],[state] FROM [dbo].[Goods] WHERE [Projname] = 
@Projname OR ISNULL(@Projname, N'') = N''
GO

 

方法五：

 

 

DECLARE @Projname NVARCHAR(10) = N'A項目'
SELECT [Projname],[version],[state] FROM [dbo].[Goods] WHERE [Projname] = @Projname
GO


DECLARE @Projname NVARCHAR(10) = NULL
SELECT [Projname],[version],[state] FROM [dbo].[Goods] WHERE [Projname] =
 IIF(@Projname IS NULL, [Projname], @Projname)
GO

 

方法六：

 

DECLARE @Projname NVARCHAR(10) = N'A項目'
SELECT [Projname],[version],[state] FROM [dbo].[Goods] WHERE [Projname] = @Projname
GO

DECLARE @Projname NVARCHAR(10) = NULL

IF LEN(ISNULL(@Projname,'')) > 0
    SELECT [Projname],[version],[state] FROM [dbo].[Goods]  WHERE [Projname] = @Projname
ELSE
    SELECT [Projname],[version],[state] FROM [dbo].[Goods]
GO