Carmen,

>... member who brought the most member join into the club. I open a table which have two column in such as member code and introducer.

This is not tested but try something like this

select INTRODUCER, count(MEMBER) as MembersRecruted;
  from <MyTable>;
   group by INTRODUCER;
    order by 2 desc;
     into cursor SELECTION

browse normal 

The first record will be the one with the most members. If You only want this one
You can also add the top clause

  select Top 1 INTRODUCER ....

HTH