Test for BUG#6495.

The bug itself is fixed by WL#2486.


mysql-test/r/select.result:
  Test for BUG#6495.
mysql-test/t/select.test:
  Test for BUG#6495.

mysql-test/r/select.result

@@ -2875,3 +2875,15 @@ b	a	t1_val	t2_val
 1	1	1	1
 1	2	2	1
 drop table t1, t2, t3;
+create table t1 (a char(1));
+create table t2 (a char(1));
+insert into t1 values ('a'),('b'),('c');
+insert into t2 values ('b'),('c'),('d');
+select a from t1 natural join t2;
+a
+b
+c
+select * from t1 natural join t2 where a = 'b';
+a
+b
+drop table t1, t2;

mysql-test/t/select.test

@@ -2443,3 +2443,16 @@ insert into t3 values (1,1),(2,1),(3,1),(4,1);
 select * from t1 natural join t2 natural join t3;
 select * from t1 natural join t3 natural join t2;
 drop table t1, t2, t3;
+
+
+#
+# Bug #6495 Illogical requirement for column qualification in NATURAL join
+#
+
+create table t1 (a char(1));
+create table t2 (a char(1));
+insert into t1 values ('a'),('b'),('c');
+insert into t2 values ('b'),('c'),('d');
+select a from t1 natural join t2;
+select * from t1 natural join t2 where a = 'b';
+drop table t1, t2;