protected function buildTblConst()/*# : array */
    {
        $result = $this->buildCol();

        // primary
        if (isset($this->tbl_constraint['primary'])) {
            $p = $this->tbl_constraint['primary'];
            $result[] = 'PRIMARY KEY (' .
                join(', ', $this->quoteIndex($p[0])) . ')' .
                (empty($p[1]) ? '' : " $p[1]");
        }

        // unique
        if (isset($this->tbl_constraint['unique'])) {
            foreach ($this->tbl_constraint['unique'] as $uniq) {
                $result[] = 'UNIQUE (' .
                    join(', ', $this->quoteIndex($uniq[0])) . ')' .
                    (empty($uniq[1]) ? '' : " $uniq[1]");
            }
        }

        // other constraints
        if (isset($this->tbl_constraint['other'])) {
            foreach ($this->tbl_constraint['other'] as $const) {
                $result[] = $const;
            }
        }

        return $result;
    }