存储过程的小错误，散分（显示是isnull附近的错误）

[chenminer]

--------------------------------------------------
-- GetTaskInfoByMultiCondition 按多个信息返回任务信息（是否打印，任务单编号，项目名称）
--------------------------------------------------
CREATE PROCEDURE GetTaskInfoByMultiCondition
@condition_1 nvarchar(50), --taskid
@condition_2 nvarchar(50), --ifprinted
@condition_3 nvarchar(50), --project_item_id
@condition_4 nvarchar(50) --exam_date
AS
SET NOCOUNT ON
declare @sql nvarchar(400)
set @sql='SELECT task_id,project_name,consign_firm,exam_date,printed_date,ifprinted FROM grosstask WHERE ifexam=1 '
exec(@sql+isnull(@condition_1,'')+' '+isnull(@condition_2,'')+' '+isnull(@condition_3,'')+' '+isnull(@condition_4,''))

RETURN 0
--------------------------------------------------
--返回一个记录集
------------------------------------------------
GO

[DigJim]

--------------------------------------------------
-- GetTaskInfoByMultiCondition 按多个信息返回任务信息（是否打印，任务单编号，项目名称）
--------------------------------------------------
CREATE PROCEDURE GetTaskInfoByMultiCondition
@condition_1 nvarchar(50), --taskid
@condition_2 nvarchar(50), --ifprinted
@condition_3 nvarchar(50), --project_item_id
@condition_4 nvarchar(50) --exam_date
AS
SET NOCOUNT ON
declare @sql nvarchar(400)
set @sql='SELECT task_id,project_name,consign_firm,exam_date,printed_date,ifprinted FROM grosstask WHERE ifexam=1 '


set @condition_1=isnull(@condition_1,'')
set @condition_2=isnull(@condition_2,'')
set @condition_3=isnull(@condition_3,'')
set @condition_4=isnull(@condition_4,'')

exec(@sql+@condition_1+@condition_2+@condition_3+@condition_4)

RETURN 0

--------------------------------------------------
--返回一个记录集
------------------------------------------------
GO