SELECT alias2.f3 AS field1 , alias2.f1 AS field2 FROM t1 AS alias1 JOIN t1 AS alias2 ON alias2.f1 = alias1.f2 AND alias2.f1 != alias1.f4 GROUP BY field1 , field2 ;
SELECT alias2.f3 AS field1 , alias2.f1 AS field2 FROM t1 AS alias1 JOIN t1 AS alias2 ON alias2.f1 = alias1.f2 AND alias2.f1 != alias1.f4 GROUP BY field1 , field2 ;