sql server 与oracle sql 不同

1.sql server 函数中的 is  returns,

        create function f_check()
          returns  int
              as
           begin
                  declare @count int
                   select @count=count(S#)  from student   group by C#
                   return @count
            end
             go

    oracle sql 函数中是 is return

      function Get_Mid_Datetime_Number(v_serial_sn in varchar2)
    return number  is
         v_sql            number;
  begin
      select count(S#) into v_sql  from student   group by C#;
       return v_sql ;
  end Get_Mid_Datetime_Number;

2. sql server 没有rownum 用 top1-n

select   top 1 y.Supplier# as supplier   from buy as x,goods as y  where  x. G# in(
select G# from goods where Gtype='牙膏')
 and y.G#=x.G# 
group by  y.Supplier#