src/db/BuildSql.php
public function column($field = '')
    {

        if ($field) {
            $this->field($field);
        }

        $this->bulidSql('SELECT');

        $result = $this->query();

        while ($row = $result->fetch(PDO::FETCH_NUM)) {
            if (count($this->options['field']) == 2) {
                $data[$row[1]] = $row[0];
            } else {
                $data[] = $row[0];
            }
        }

        return isset($data) ? $data : [];
    }
public function column($field = '')
    {

        if ($field) {
            $this->field($field);
        }

        $this->bulidSql('SELECT');

        $result = $this->query();

        while ($row = $result->fetch(PDO::FETCH_NUM)) {
            if (count($this->options['field']) == 2) {
                $data[$row[1]] = $row[0];
            } else {
                $data[] = $row[0];
            }
        }

        return isset($data) ? $data : [];
    }
获取单个字段列表
@date   2018-07-12T14:41:02+0800
@author ChenMingjiang
@param  [type]                   $field [description]
@return [type]                          [description]