SQL Server存儲過程sp_executesql

Question

我有這個存儲過程

USE [all_things] 
GO 
SET ANSI_NULLS ON 
GO 
SET QUOTED_IDENTIFIER ON 
GO 

ALTER PROCEDURE [dbo].[sp_getThingsByType] 
    @thingid int, 
    @typeid int 
AS 

DECLARE @Sql NVARCHAR(MAX) = 'SELECT * from items' 

IF @thingid IS NOT NULL 
BEGIN 
    SET @Sql += ' where thingid = @thingid' 
END 

IF @typeid IS NOT NULL 
BEGIN 
    SET @Sql += ' and TypeID = @typeid' 
END 

EXEC sp_executesql @sql, N'@thingid int,@typeid int',@thingid=@thingid,@typeid=@typeid; 

測試用例：

1. 當我運行它thingid是null和typeid是null，我得到的所有結果是完善。

2. 當thingid供應和typeid是null，結果是OK

3. 這裏是哪裏，結果並不好：thingid是null和typeid供應。一切都被退回。

我錯過了什麼？

謝謝

Answer 1

感謝@ tschmit007，我修好了。

USE [all_things] 
GO 
SET ANSI_NULLS ON 
GO 
SET QUOTED_IDENTIFIER ON 
GO 

ALTER PROCEDURE [dbo].[sp_getThingsByType] 
    @thingid int, 
    @typeid int 
AS 

DECLARE @Sql NVARCHAR(MAX) = 'SELECT * from items' 

IF @thingid IS NOT NULL 
BEGIN 
    SET @Sql += ' where thingid = @thingid' 
END 

IF @typeid IS NOT NULL AND @thingid IS NOT NULL 
BEGIN 
    SET @Sql += ' and TypeID = @typeid' 
END 

IF @typeid IS NOT NULL AND @thingid IS NULL 
BEGIN 
    SET @Sql += ' where TypeID = @typeid' 
END 

EXEC sp_executesql @sql, N'@thingid int,@typeid int',@thingid=@thingid,@typeid=@typeid;