Merge pull request rails#6698 from yahonda/address_ora_911_master

Address ORA-00911 errors because of the heading underscore.

Author: rafaelfranca

activerecord/lib/active_record/relation/finder_methods.rb

@@ -176,7 +176,7 @@ def exists?(id = false)
 
       join_dependency = construct_join_dependency_for_association_find
       relation = construct_relation_for_association_find(join_dependency)
-      relation = relation.except(:select, :order).select("1 AS _one").limit(1)
+      relation = relation.except(:select, :order).select("1 AS one").limit(1)
 
       case id
       when Array, Hash

activerecord/test/cases/finder_test.rb

@@ -46,7 +46,7 @@ def test_exists
   end
 
   def test_exists_does_not_select_columns_without_alias
-    assert_sql(/SELECT\W+1 AS _one FROM ["`]topics["`]\W+LIMIT 1/) do
+    assert_sql(/SELECT\W+1 AS one FROM ["`]topics["`]/i) do
       Topic.exists?
     end
   end