用PHP开始你的MVC (二)抽象数据库接口(4)

    function getSeq($fieldName, $step=1, $start=1){
        $table = DB_SEQUENCE_TABLENAME;
        $step = (int)$step;
        $start = (int)$start;
        $rs = mysql_query("UPDATE $table SET seq_num=seq_num+($step) WHERE seq_name='$fieldName'");
        if(!$rs || mysql_affected_rows($this->cnn)<1){
            $rs = mysql_query('SELECT * FROM '.DB_SEQUENCE_TABLENAME, $this->cnn);
            if(!$rs){
                $sql = "CREATE TABLE $table (
                               seq_name VARCHAR( 20 ) NOT NULL ,
                               seq_num BIGINT( 20 ) DEFAULT 1 NOT NULL ,
                               PRIMARY KEY (seq_name))";
                $rs = mysql_query($sql) or $this->_halt('创建序列发生器表失败', $sql);
            }
            $rs = mysql_query("INSERT INTO $table VALUES('$fieldName', $start)") or
                       $this->_halt('添加新序列错误', $sql);
            $seq = $start;
        }else{
            $seq = &$this->getOne("SELECT seq_num FROM $table WHERE seq_name='$fieldName'");
        }
        return $seq;
    }

    function _getCommand($fetchType){
        switch($fetchType){
            case DB_FETCH_ASSOC: $exe = 'mysql_fetch_assoc'; break;
            case DB_FETCH_NUM: $exe = 'mysql_fetch_row'; break;
            case DB_FETCH_BOTH: $exe = 'mysql_fetch_array'; break;
            case DB_FETCH_OBJECT: $exe = 'mysql_fetch_object'; break;
            default: $exe = 'mysql_fetch_array'; break;
        }
        return $exe;
    }

    function _halt($msg){
        $errNo = mysql_errno($this->cnn);
        $errStr = mysql_error($this->cnn);
        die("数据库错误：$msg<br> $errNo : $errStr");
    }
}
?>