自己写了一个存储过程，为什么insert into dbo.TB_InventoryInfo(CommodityID,WarehouseID,Quantity,
ALTER PROCEDURE [dbo].[addTB_IncomInfo] 
(
@CommodityID int,
@WarehousePeople  nvarchar(30),
@WarehouseID int,
@ArrivalDate datetime,
@StorageDate datetime,
@CommodityQuanlity float,
@Remark nchar(10)=null,
@unit nvarchar(20),
@returnvalue int=1 output)
AS
declare @s float
 set @s=(select [Quantity] from dbo.TB_InventoryInfo where CommodityID=@CommodityID and WarehouseID=@WarehouseID)
if @s=null
 begin 
 insert into dbo.TB_IncomInfo(CommodityID,WarehousePeople,WarehouseID,ArrivalDate,StorageDate,CommodityQuanlity,unit,Remark)
 values(@CommodityID,@WarehousePeople,@WarehouseID,@ArrivalDate,@StorageDate,@CommodityQuanlity,@unit,@Remark)
 insert into dbo.TB_InventoryInfo(CommodityID,WarehouseID,Quantity,Unit) 
 values(@CommodityID,@WarehouseID,@CommodityQuanlity,@unit)
 set @returnvalue=0
 end
else 
 begin
 update dbo.TB_InventoryInfo set Quantity=Quantity+@CommodityQuanlity where CommodityID=@CommodityID and WarehouseID=@WarehouseID
 insert into dbo.TB_IncomInfo(CommodityID,WarehousePeople,WarehouseID,ArrivalDate,StorageDate,CommodityQuanlity,unit,Remark)
 values(@CommodityID,@WarehousePeople,@WarehouseID,@ArrivalDate,@StorageDate,@CommodityQuanlity,@unit,@Remark)
 set @returnvalue=0
 end
以上就是我写的一个存数过程，别的地方都没问题，为什么insert into dbo.TB_InventoryInfo(CommodityID,WarehouseID,Quantity,Unit) 
 values(@CommodityID,@WarehouseID,@CommodityQuanlity,@unit)这一句每次运行后，都不能在数据库插入数据，
------解决方案--------------------
if @s=null
我觉得这句有问题，如果查询为空应该为@s is null
吧
------解决方案--------------------
1楼已经点明问题所在。

你这写法，第一个分支永远不会进去。