CodeIgniter - 当secound表中没有行时,MySQL连接

Question

我在模型中有这个查询:

  public function Games() {
    $q = $this->db->select('games.id, games.title, games.slug, games.dev_id, games.dev, games.plat_id, games.plat');
    $q = $this->db->from('games');
    $q = $this->db->join('rates', 'games.id = rates.game_id');
    $q = $this->db->select_avg('rates.rate');
    $q = $this->db->get();

    return $q->result();
}

我的目标是列出所有内容games,另外rate从rates可用时获得平均值.现在它只显示两个表中的那些行.我怎么解决这个问题？

Answer 1

使用此说明

$this->db->select('games.id, games.title, games.slug, games.dev_id, games.dev, games.plat_id, games.plat');
$this->db->select_avg('rates.rate');
$this->db->from('games');
$this->db->join('rates', 'games.id = rates.game_id','left');
$this->db->group_by('rates.game_id');
$q = $this->db->get();

左连接将带来多个结果.使用avg和group by将限制为每条记录只获取一行.