Use something like:

select  distinct (s.C)
  from  TTTT as t, TTTT as s    
 where  something
        and s.A = t.A 
        and s.B = t.B;
[download]

This is the SQL dialect that MySQL speaks. For Sybase, you would probably use something like:

select  distinct (s.C)
  from  TTTT.t, TTTT.s          
 where  something
        and s.A = t.A 
        and s.B = t.B;
[download]

But I don't have a server to test this on.

You might want to edit the "something" to explicitely mention the table alias t.

Abigail