-1

我是使用 sql 的新手，但我有一个似乎无法解决的问题。我有四个表：T_Item、t_trade、T_sender_trade 和 T_receiver_trade，如下所示：

T_Item
(itemID, name, category, description, description);

T_Trade
(tradeID, date, senderID, receiverID);

T_sender_trade
(tradeID, senderItemID) - both foreign keys from the previous tables

T_receiver_trade
(tradeID, receiverItemID) - as in T_sender_trade

这意味着发送者和接收者交易两个项目。我想要做的是用 php 在 html 中创建一个表，其中包含以下信息：

  • 发件人对物品的描述
  • 收货人对物品的描述
  • 日期（交易日期）

我正在使用老师要求的课堂交易。我在课堂上使用了以下代码：

<?php
    require_once '../utils/ligabd.php'; (uses the connection to the mysql in another class)

Class Trade
    {
            public $tradeID;
        public $date;
        public $senderID;
        public $receiverID


        public function __construct($date = null, $senderID= null, $receiverID=null) {

            $this->date= $date;
                $this->senderID= $senderID;
            $this->receiverID= $receiverID;     
                                }

    public static function load($tradeID) {
    $result = mysql_query("SELECT * FROM T_Trade");
    if (!$result) {
        die('Troca não existente ' . mysql_error());
    }
    $row = mysql_fetch_assoc($result);
    if ($row) {
      $t = new Trade();
      $t->tradeID = $row["tradeID"];
      $t->date = $row["date"];
      $t->senderID=$row["senderID"];
      $t->receiverID=$row["receiverID"];
      return $t;
    } else {
      return NULL;
    }
    }

public static function returnsSenderItem($tradeID) {
    $result = mysql_query("SELECT * FROM T_Item, T_sender_trade where T_sender_trade.tradeID= $tradeID AND T_sender_trade.senderItemID =T_Item.ItemID");

if(!$result) {
die ('Trade not found ' .mysql_error());
}
$rows=Array();
    while ($row = mysql_fetch_assoc($result)) {
    $rows[]=$row;
            }
            return $rows;
            }

接收者的物品也是如此。在我使用的 php 代码中（只是为了获得一个项目的描述，因为我能够获得 ttade 的日期）：

include '../classes/troca.php';
$tradeID=$_GET[tradeID];
$trade=Trade::load($tradeID);
echo $trade->date; 
$sender=Trade::returnsSenderItem($tradeID);
foreach($senderr as $s):
echo $s['name'];
endforeach;

我应该使用这样的代码来制作我的桌子。问题是程序无法从 T_Item 中找到数据。我应该在我的类/php 中进行哪些更改，这样才能做到？谢谢你。

4

1 回答 1

0

为了获得发送者和接收者项目的描述，您需要链接到 T_Item 表两次（每个项目一次） - 这将需要使用表别名，如下所示：

select t.tradeID,
       t.`date`,
       t.senderID,
       s.SenderItemID,
       si.description as SenderDescription,
       t.receiverID,
       r.ReceiverItemID,
       ri.description as ReceiverDescription
from T_Trade as t
join T_sender_trade as s on t.tradeID = s.tradeID
join T_Item as si on s.senderItemID = si.itemID
join T_receiver_trade as r on t.tradeID = r.tradeID
join T_Item as ri on s.receiverItemID = ri.itemID
where t.tradeID = $tradeID
于 2013-05-23T18:01:20.297 回答