sql - Select rows where some values are not in other table -

a , b of table t3 same , b t1. need select values aren't on t3. if there line a,b on t3 don't wanna show it.

select t1.a, t1.b, t1.c t1, t2 t1.x=t2.x , not exists (    select t3.a, t3.b    t3 ) 

any help? thanks

select t1.a, t1.b, t1.c t1 inner join t2 on t1.x=t2.x not exists (    select 1 t3    t3.a = t1.a , t3.b = t1.b )