如何在Codeigniter中减去两个日期（从数据库的2列中）

Question

我必须在模型中进行查询，以便通过两个日期之间的这种减法进行排序。 我必须计算ordersheader.transportDate和orderitems.forecast_hour列之间的减法。 它们在2个表中ordersheader和orderitems 。 我在idOrder加入了他们。
首先，我必须为每个idOrder找到max（ orderitems.forecast_hour ），然后从orderitems.forecast_hour为每个idOrder减去ordersheader.transportDate这个最大值。 因为它是同一日期，所以应该以小时为单位进行计算。 它应该首先显示，这些idOrders为orderitems.transportDate此最大orderitems.forecast_hour <0。我尝试过此操作，但它给了我错误：

Call to undefined function DATEDIFF

何去做？

<?php
 function getOrders(){
            $date = new DateTime("now");
            $curr_date = $date->format('Y-m-d');
            $this->db->select('orderitems.eggSize as size');
            $this->db->select('ordersheader.*,customer.name,GROUP_CONCAT(orderitems.itemNumber) as itemNumber');
            $this->db->select('ordersheader.*,customer.name,ordersheader.*,customer.name,GROUP_CONCAT(orderitems.quantity ) as quantity ');
            $this->db->select('ordersheader.*,customer.name,ordersheader.*,customer.name,GROUP_CONCAT(orderitems.unitPrice) as unitPrice');
            $this->db->select('ordersheader.*,customer.name,ordersheader.*,customer.name,GROUP_CONCAT(orderitems.eggSize ) as eggSize');
            $this->db->select('GROUP_CONCAT(orderitems.forecast_hour) as forecast_hour');
            $this->db->from('ordersheader'); 
            $this->db->join('orderitems', 'orderitems.idOrder = ordersheader.idOrder');
            $this->db->join('customer', 'customer.idCustomer = ordersheader.idCustomer');
            $this->db->where('DATE(orderDueDate)', $curr_date);
            $this->db->group_by('orderitems.idOrder');
            $this->db->order_by(DATEDIFF('hour', 'ordersheader.transportDate', 'orderitems.forecast_hour'));
            $query = $this->db->get();
            return $query->result();
        }

Answer 1

请尝试以下更改。 DATEDIFF必须在您的SELECT行中：

$date = new DateTime("now");
$curr_date = $date->format('Y-m-d');
$this->db->select('orderitems.eggSize as size');
$this->db->select('DATEDIFF("hour", "ordersheader.transportDate", "orderitems.forecast_hour") AS MyDateDiff'); //ADD THIS
$this->db->select('ordersheader.*,customer.name,GROUP_CONCAT(orderitems.itemNumber) as itemNumber');
$this->db->select('ordersheader.*,customer.name,ordersheader.*,customer.name,GROUP_CONCAT(orderitems.quantity ) as quantity ');
$this->db->select('ordersheader.*,customer.name,ordersheader.*,customer.name,GROUP_CONCAT(orderitems.unitPrice) as unitPrice');
$this->db->select('ordersheader.*,customer.name,ordersheader.*,customer.name,GROUP_CONCAT(orderitems.eggSize ) as eggSize');
$this->db->select('GROUP_CONCAT(orderitems.forecast_hour) as forecast_hour');
$this->db->from('ordersheader');
$this->db->join('orderitems', 'orderitems.idOrder = ordersheader.idOrder');
$this->db->join('customer', 'customer.idCustomer = ordersheader.idCustomer');
$this->db->where('DATE(orderDueDate)', $curr_date);
$this->db->group_by('orderitems.idOrder');
$this->db->order_by(MyDateDiff); //EDIT THIS

$query = $this->db->get();
return $query->result();