sql server 备份表数据，更新到原表（动态语句拼接）

declare @sql varchar(max)
select @sql=isnull(@sql+',','')+name+'='+'b.'+name from syscolumns 
where id=OBJECT_ID('a') and name<>'ID'
set @sql=
'update a
set '+@sql+'
from a a,a_backup b
where a.ID=b.ID'

exec (@sql)