SELECT * FROM table1
WHERE * NOT IN (SELECT * FROM table2);
select t1.*, t2.*
from table1 t1
join table2 t2 on t2.field1 = t1.field1
and t2.field2 = t1.field2
and ... -- сравниваем все поля
select t1.* from table1 t1
UNION
select t2.* from table2 t2
MINUS
select t1.*
from table1 t1
join table2 t2 on t2.field1 = t1.field1
and t2.field2 = t1.field2
and ... -- сравниваем все поля