Codeigniter中如何在没有条件的情况下选择联接多个表？

问题描述：

我想在codeigniter中使用join选择多个表，但是我不想在下面的代码中添加任何条件

I want to select multiple table using join in codeigniter but I don't want to make any conditional as below code

public function get_invoice(){

    $this->db->select('isp.*,dp.*,ip.*'); 
    $this->db->from('isp');
    $this->db->join('dp','dp.status = isp.status');
    $this->db->join('isp','isp.status = ip.status');
    $this->db->limit(5000);
    $this->query =  $this->db->get();
    if($this->query->num_rows()>0){
        return $this->query->result();
    }

}

但是我想获取所有数据

那我该如何在无条件的情况下从多个表中选择数据？

感谢帮助

答

是的，您可以无条件加入查询。内左右联接需要条件。因此，您可以执行交叉联接。就像这样

Yes you can join query without condition. INNER LEFT RIGHT JOINS need condition.So you can do Cross JOIN.LIKE this

public function get_invoice(){

 $this->db->select('isp.*,dp.*,ip.*'); 
 $this->db->from('isp,dp,ip');
 $this->db->limit(5000);
 $this->query =  $this->db->get();
 if($this->query->num_rows()>0)
 {
    return $this->query->result();
 }

}

但是如果您的isp在Cross JOIN有100条记录，dp有20条记录，ip有50条记录它将产生（100 * 20 * 50）条记录。希望您知道CROSS，LEFT，INNER，RIGHT JOIN的作用。

But at Cross JOIN if your isp has 100,dp has 20, and ip has 50 record It will produce (100*20*50) record.I hope you know what CROSS,LEFT,INNER,RIGHT JOIN do.

Codeigniter中如何在没有条件的情况下选择联接多个表？

相关推荐