以下代码按预期工作：
在控制器中

public function generatereport(){
        // Set Page Title
        $this->data['page_title'] = 'Generate Report';
        $this->data['reports'] = null;

        $rules = $this->support_m->rules_report;
        $this->form_validation->set_rules($rules);

        $startdate = $this->input->post('startdate');
        $enddate = $this->input->post('enddate');

        if ($this->form_validation->run() == TRUE){
            $results = $this->db->select('location, count(location) as locationcount, AVG(review) as reviewavg')
            ->where('datesubmitted BETWEEN "'.$startdate.'" AND "'.$enddate.'"')
            ->group_by('location') 
            ->get('tickets')->result();
            $this->data['reports'] = $results;
        }

        // Load view    
        $this->data['subview'] = 'admin/tickets/report';
        $this->load->view( 'admin/body', $this->data );

    }

在视图中

<table class="table table-striped">
                    <thead>
                        <tr>
                            <th>Location</th>
                            <th>Total Tickets</th>
                            <th>Avg Review</th>
                        </tr>
                    </thead>
                    <tbody>
                        <?php 
                            if(count($reports)): foreach($reports as $ticketreport): 
                        ?>
                        <tr>
                            <td><?php echo $ticketreport->location; ?></td>
                            <td><?php echo $ticketreport->locationcount; ?></td>
                            <td><?php echo $ticketreport->reviewavg; ?></td>
                        </tr>
                        <?php endforeach; ?>
                        <?php else: ?>
                            <tr>
                                <td colspan="4">We could not find any records.</td>
                            </tr>
                            <?php endif; ?> 
                    </tbody>
                </table>

感谢所有的贡献者。

如果我知道你想要什么，像这样的东西可以帮助你：

SELECT location, COUNT(location) as location_count, AVG(review) as review_avg
FROM progrodb.tickets
WHERE datesubmitted BETWEEN '2018-09-01' AND '2018-09-30'
GROUP BY location

为了便于阅读，我把计数和平均值取了个别名

我想你需要这样的短信

SELECT location, COUNT(location), AVG(review) 
FROM progrodb.tickets
WHERE datesubmitted BETWEEN '2018-9-1' AND '2018-9-30'
GROUP BY location = 'location'

我想你需要having子句来表示聚合函数。像这样的方法可能有用：

SELECT
    location,
    COUNT( location ),
    AVG( review ) 
FROM
    progrodb.tickets 
WHERE
    datesubmitted BETWEEN '2018-9-1' 
    AND '2018-9-30' 
HAVING
    location = 'location'

您可以使用以下方法为多个位置生成报告：

$results = $this->db->select('count(location), AVG(review)')
   ->where('datesubmitted BETWEEN "2018-9-1" AND "2018-9-30"')
   ->group_by('location') 
   ->get('tickets')->result();