简单的存储过程，看看错在哪里呢？
ALTER PROCEDURE get_paper_id
@course varchar(30),
@year numeric(4,0),
@semester varchar(8),
@paper_name varchar(100)
AS
declare @sql nvarchar(100)
declare @id varchar(10)
begin
set @sql='select @id=id from paper where 课程='''+@course+'''
and 年份='''+@year+''' and 学期='''+@semester+''' and 试题='''+@paper_name+''''
exec sp_executesql @sql
end
RETURN @id

[解决办法]