Codeigniter 活动记录 COUNT 返回 null答案

【问题标题】：Codeigniter active record COUNT return nullCodeigniter 活动记录 COUNT 返回 null
【发布时间】：2019-02-07 05:21:16
【问题描述】：

我需要从一个表中选择一些数据并从另一个表中计算相关图像。我正在使用的代码如下（来自模型文件）

$this->rci_db->select (" 
        $this->tbl_register.id,
        $this->tbl_register.cor,
        DATE_FORMAT($this->tbl_register.registerdate, '%d/%m/%Y') AS registerdate,
        $this->tbl_registrations.registration,
        $this->tbl_aircrafts.cn,
        $this->tbl_aircrafts.built,
        $this->tbl_manufacturers.manufacturer, 
        $this->tbl_models.type AS model,
        COUNT($this->tbl_images.imgid) AS count
        ");
    $this->rci_db->from("$this->tbl_register");
    $this->rci_db->join("$this->tbl_registrations", "$this->tbl_registrations.rid = $this->tbl_register.rid", 'left');
    $this->rci_db->join("$this->tbl_aircrafts", "$this->tbl_register.aid = $this->tbl_aircrafts.aid", 'left');
    $this->rci_db->join("$this->tbl_manufacturers", "$this->tbl_manufacturers.mid = $this->tbl_aircrafts.mid", 'left');
    $this->rci_db->join("$this->tbl_models", "$this->tbl_models.tid = $this->tbl_aircrafts.tid", 'left');
    $this->rci_db->join("$this->tbl_images", "$this->tbl_register.id = $this->tbl_images.id", 'left');

    $this->rci_db->where("$this->tbl_register.rid", $rid);

    $query = $this->rci_db->get();

    if ($query->num_rows() > 0)
    {
        return $query->result();
    }
    return false;

查询为 COUNT 语句返回 null，我无法找出问题所在。其他数据正确返回感谢您的帮助。

【问题讨论】：

标签： mysql codeigniter count

【解决方案1】：

该计数在另一个表中，因此您必须在查询中以某种方式关联这些计数。而不是在这种情况下加入，只使用子选择可能很容易。

在你的选择中有这样的东西：

$this->rci_db->select (" 
        $this->tbl_register.id,
        $this->tbl_register.cor,
        DATE_FORMAT($this->tbl_register.registerdate, '%d/%m/%Y') AS registerdate,
        $this->tbl_registrations.registration,
        $this->tbl_aircrafts.cn,
        $this->tbl_aircrafts.built,
        $this->tbl_manufacturers.manufacturer, 
        $this->tbl_models.type AS model,
        (SELECT COUNT($this->tbl_images.imgid) FROM $this->tbl_images WHERE $this->tbl_register.id = $this->tbl_images.id) AS count
        ");

【讨论】：