Replace drop sql statement to drop_table method

to drop sequences at the same time each tables dropped for Oracle

activerecord/test/cases/associations/required_test.rb

@@ -18,8 +18,8 @@ class Child < ActiveRecord::Base
   end
 
   teardown do
-    @connection.execute("DROP TABLE parents") if @connection.table_exists? 'parents'
-    @connection.execute("DROP TABLE children") if @connection.table_exists? 'children'
+    @connection.drop_table 'parents' if @connection.table_exists? 'parents'
+    @connection.drop_table 'children' if @connection.table_exists? 'children'
   end
 
   test "belongs_to associations are not required by default" do

activerecord/test/cases/attribute_decorators_test.rb

@@ -28,7 +28,7 @@ def type_cast_from_user(value)
 
     teardown do
       return unless @connection
-      @connection.execute 'DROP TABLE attribute_decorators_model' if @connection.table_exists? 'attribute_decorators_model'
+      @connection.drop_table 'attribute_decorators_model' if @connection.table_exists? 'attribute_decorators_model'
       Model.attribute_type_decorations.clear
       Model.reset_column_information
     end

activerecord/test/cases/migration/foreign_key_test.rb

@@ -29,8 +29,8 @@ class Astronaut < ActiveRecord::Base
 
       teardown do
         if defined?(@connection)
-          @connection.execute "DROP TABLE astronauts" if @connection.table_exists? 'astronauts' 
-          @connection.execute "DROP TABLE rockets" if @connection.table_exists? 'rockets'
+          @connection.drop_table "astronauts" if @connection.table_exists? 'astronauts' 
+          @connection.drop_table "rockets" if @connection.table_exists? 'rockets'
         end
       end