select * from t2

C1 C2          C3        
-- ----------- -----------
1            1           1
1            1           2
2            1           1
3            1           1

select t1.c1,c2,c3 
  from t1 left join t2 on t1.c1=t2.c1

C1 C2          C3        
-- ----------- -----------
1            1           1
1            1           2
3            1           1
4            -           -

select t1.c1, c2, c3 
  from t1 
         left join
           (select t1.c1,max(c2) c2,max(c3) c3 
               from t1,t2 where t1.c1=t2.c1 
            group by t1.c1 )t2 on t1.c1=t2.c1

C1 C2          C3        
-- ----------- -----------
1            1           2
3            1           1
4            -           -