private function getColumnConstraintSQL($table, $column)
    {
        return "SELECT SysObjects.[Name]
            FROM SysObjects INNER JOIN (SELECT [Name],[ID] FROM SysObjects WHERE XType = 'U') AS Tab
            ON Tab.[ID] = Sysobjects.[Parent_Obj]
            INNER JOIN sys.default_constraints DefCons ON DefCons.[object_id] = Sysobjects.[ID]
            INNER JOIN SysColumns Col ON Col.[ColID] = DefCons.[parent_column_id] AND Col.[ID] = Tab.[ID]
            WHERE Col.[Name] = " . $this->_conn->quote($column) . ' AND Tab.[Name] = ' . $this->_conn->quote($table) . '
            ORDER BY Col.[Name]';
    }