Question

我遇到了加入mysql的问题，我试图在订单表中的band_id与来自band表的Band_id匹配时，将order表中的Name字段填充到orders表中的band_name字段。这一切都令人困惑，并希望得到一些建议或帮助。

我的代码

 <?php
        }   

        $user = new User();
        $user_name = escape($user->data()->username);

        $result = mysql_query("SELECT bands.Name FROM bands LEFT JOIN orders ON bands.Band_id = orders.band_id WHERE orders.band_id = 1 AND user_name = '"mysql_real_escape_string($user_name)"'");
       //$result = mysql_query("SELECT * FROM orders WHERE user_name = '".mysql_real_escape_string($user_name)."'");


        echo '<table border="1">
        <tr>
        <th>My bookings</th>
        <th>gig No</th>
        </tr>';

        if(mysql_num_rows($result) > 0){
            while($row = mysql_fetch_array($result)){
                echo 
                "<tr>
                <td>".$row['user_name']."</td>
                <td>".$row['band_id']."</td>
                </tr>";
            }
        }else{
            echo "<tr><td>No bookings</td></tr>";
        }
        echo "</table>";
        ?>

Answer 1

SELECT * FROM bands
LEFT JOIN orders as user_orders ON(
user_orders.band_id = bands.band_id
AND user_orders.user_name = "'.mysql_real_escape_string($user_name).'"
)

Answer 2

我认为你接近你对DB的使用有点不对。

您的bands表格应包含乐队所需的所有信息。比如这个：

| id | name        |
====================
| 1  | The Beatles |
| 2  | Blur        |
etc

您的orders表应包含所有或您的订单数据：

| id | band_id |
================
| 1  | 2       |
| 2  | 1       |
| 3  | 1       |

如你所见，甲壳虫乐队有2个订单，Blur有1个订单。

你可以获得这样的订单的乐队名称：

SELECT bands.name FROM orders, bands, WHERE orders.id = 1 AND orders.band_id = bands.id;

使用内部联接：

SELECT bands.name FROM bands INNER JOIN orders ON bands.id = orders.band_id WHERE orders.id = 1;

使用左连接：

SELECT bands.name FROM bands LEFT JOIN orders ON bands.id = orders.band_id WHERE orders.id = 1;

更新：

有关联接的更多详细信息，请参阅此图像：

SQL join examples

取自this stack overflow question。

Mysql加入表之间的共享数据

2 个答案: