mysql gå med i 3 tabeller

 SELECT t1.a, t1.b, t2.c, t2.d, t3.e, t3.f
  FROM table1 t1
  JOIN table2 t2 ON (t1.id = t2.id) 
  JOIN table3 t3 ON (t1.id = t3.id)
  ORDER BY t1.id;