Question

我是使用sql的新手，但我遇到了一个我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

这意味着发件人和收件人交易两件商品。我想要做的是使用php在html中创建一个表，其中包含以下信息：

来自发件人的项目说明
来自接收者的项目描述
日期（交易日期）

我正在使用班级交易，因为我的老师要求。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;
            }

对于接收者的项目也一样。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表格。事情是程序无法从T_Item中找到数据..我应该在我的类/ php中更改它应该怎么做？谢谢。

Answer 1

为了获得发件人和收件人项目的描述，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，如此：

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

从mysql表中获取值

1 个答案: