利用时间函数修改数据库中的时间节点

declare @code varchar(1)
set @code = '0-20150809318'
select BeginTime from worksheet where code = @code and StateType = '机修上线'
select * from dba_para where para_code = @code
update dba_para set para_time_end = dateadd(n,1,(select BeginTime from worksheet where code = @code and StateType = '机修上线')) where para_code = @code and para_time_end != ''
select * from dba_para where para_code = @code
我想把机修上线的时间节点往前提前但是不行啊请大神指教