Fix for BUG#6276.

mysql-test/r/select.result:
  Test for BUG#6276.
mysql-test/t/select.test:
  Test for BUG#6276.
sql/sql_base.cc:
  Add a true ON condition for outer joins without common columns.

mysql-test/r/select.result

@@ -2829,3 +2829,34 @@ Warnings:
 Warning	1292	Truncated incorrect DOUBLE value: 'x'
 drop table t1;
 drop view v1;
+create table t1(a1 int);
+create table t2(a2 int);
+insert into t1 values(1),(2);
+insert into t2 values(1),(2);
+create view v2 (c) as select a1 from t1;
+select * from t1 natural left join t2;
+a1	a2
+1	1
+1	2
+2	1
+2	2
+select * from t1 natural right join t2;
+a2	a1
+1	1
+1	2
+2	1
+2	2
+select * from v2 natural left join t2;
+c	a2
+1	1
+1	2
+2	1
+2	2
+select * from v2 natural right join t2;
+a2	c
+1	1
+1	2
+2	1
+2	2
+drop table t1, t2;
+drop view v2;

mysql-test/t/select.test

@@ -2406,3 +2406,23 @@ insert into t1 values (1,'x',5);
 select * from t1 natural join v1;
 drop table t1;
 drop view v1;
+
+#
+# Bug #6276 A SELECT that does a NATURAL OUTER JOIN without common
+#           columns crashes server because of empty ON condition
+#
+
+create table t1(a1 int);
+create table t2(a2 int);
+insert into t1 values(1),(2);
+insert into t2 values(1),(2);
+create view v2 (c) as select a1 from t1;
+
+select * from t1 natural left join t2;
+select * from t1 natural right join t2;
+
+select * from v2 natural left join t2;
+select * from v2 natural right join t2;
+
+drop table t1, t2;
+drop view v2;

sql/sql_base.cc

@@ -3851,6 +3851,11 @@ store_top_level_join_columns(THD *thd, TABLE_LIST *table_ref,
     */
     table_ref_1->natural_join= table_ref_2->natural_join= NULL;
 
+    /* Add a TRUE condition to outer joins that have no common columns. */
+    if (table_ref_2->outer_join &&
+        !table_ref_1->on_expr && !table_ref_2->on_expr)
+      table_ref_2->on_expr= new Item_int((longlong) 1,1);   /* Always true. */
+
     /* Change this table reference to become a leaf for name resolution. */
     if (left_neighbor)
     {