Fixed #20388 -- Test failures under Oracle.

    All tests in this test case are also run with settings.DEBUG=True in

    EscapingChecksDebug test case, to also test CursorDebugWrapper.

    """

    # For Oracle, when you want to select a value, you need to specify the

    # special pseudo-table 'dual'; a select with no from clause is invalid.

    bare_select_suffix = " FROM DUAL" if connection.vendor == 'oracle' else ""

    def test_paramless_no_escaping(self):

        cursor = connection.cursor()

        cursor.execute("SELECT '%s'")

        cursor.execute("SELECT '%s'" + self.bare_select_suffix)

        self.assertEqual(cursor.fetchall()[0][0], '%s')

    def test_parameter_escaping(self):

        cursor = connection.cursor()

        cursor.execute("SELECT '%%', %s", ('%d',))

        cursor.execute("SELECT '%%', %s" + self.bare_select_suffix, ('%d',))

        self.assertEqual(cursor.fetchall()[0], ('%', '%d'))

    @unittest.skipUnless(connection.vendor == 'sqlite',