CodeIgniter 中“on 子句”中的未知列“”答案

【问题标题】：Unknown column '' in 'on clause' in CodeIgniterCodeIgniter 中“on 子句”中的未知列“”
【发布时间】：2012-12-23 06:15:34
【问题描述】：

我正在尝试使用 CodeIgniter activercord 类进行连接查询，如下所示：

$query = $this->db->select('accredited_majors, all_majors_accredited, accredited')
                    ->select('universities.name, universities.slug')
                    ->from('accreditations')
                    ->join('universities', 'universities.id = '.$uni_id)
                    ->where('accreditations.university_id', $uni_id)
                    ->where('accreditations.country', $country)
                    ->get();

但我得到了这个错误：

A Database Error Occurred
Error Number: 1054

Unknown column '820' in 'on clause'

SELECT `accredited_majors`, `all_majors_accredited`, `accredited`, `default_universities`.`name`, `default_universities`.`slug` FROM (`default_accreditations`) JOIN `default_universities` ON `default_universities`.`id` = `820` WHERE `default_accreditations`.`university_id` = '820' AND `default_accreditations`.`country` = 'AE'

我相信错误出现在 join() 行中：

->join('universities', 'universities.id = '.$uni_id)

如何在 join() 函数中包含变量？

【问题讨论】：

我觉得应该是join('universities', 'universities.id = accreditations.university_id')

标签： mysql codeigniter activerecord join

【解决方案1】：

在您的代码中，您有 2 个 WHERE 子句而不是 ON，并且您的连接与 on 子句有误。

试试这个

    $query = $this->db->select('accredited_majors, all_majors_accredited, accredited')
                ->select('universities.name, universities.slug')
                ->from('accreditations')
                ->join('universities', 'universities.id = accreditations.university_id')
                ->where('accreditations.university_id', $uni_id)
                ->where('accreditations.country', $country)
                ->get();

【讨论】：

codeigniter activerecord 中是否有一个名为 ON() 的函数？这给了我这个错误：Fatal error: Call to undefined method CI_DB_mysql_driver::on()

【解决方案2】：

试试这个

$query = $this->db->select('accredited_majors, all_majors_accredited, accredited')
                    ->select('universities.name, universities.slug')
                    ->from('accreditations')
                    ->join('universities', "universities.id = accreditations.$uni_id" , 'left')
                    ->where('accreditations.university_id', $uni_id)
                    ->where('accreditations.country', $country)
                    ->get();

【讨论】：

【解决方案3】：

试试这个

$this->db->select('accredited_majors, all_majors_accredited, accredited')
->select('universities.name, universities.slug')
->from('accreditations')
->join('universities', 'universities.id = accreditations.university_id', 'left')
->where('accreditations.university_id', $uni_id)
->where('accreditations.country', $country)
->group_by('accreditations.university_id')
->get();

【讨论】：