Question

我有3个TABLES产品，products_extra_fields，products_to_products_extra_fields

产品表

+-------------+--------------+---------------+
| products_id | categories_id| products_name |
+-------------+--------------+---------------+
| 1           | 1            | product 1     |
| 2           | 1            | product 2     |
+-------------+--------------+---------------+

products_extra_fields TABLE

+--------------------------+---------------------------+
| products_extra_fields_id | products_extra_fields_name| 
+--------------------------+---------------------------+
| 1                        | sugar                     |
| 2                        | cocoa                     |
| 3                        | butter                    |
| 4                        | milk                      |
+--------------------------+---------------------------+

products_to_products_extra_fields TABLE

+-------------+---------------------------+-----------------------------+
| products_id | products_extra_fields_id  | products_extra_fields_value |
+-------------+---------------------------+-----------------------------+
| 1           | 1                         | 20%                         |
| 1           | 2                         | 45%                         |
| 1           | 3                         | 27%                         |
| 2           | 1                         | 12%                         |
+-------------+---------------------------+-----------------------------+

我想编辑产品1 我使用此查询：

SELECT 
products_name, 
products_extra_fields_name, 
products_extra_fields_value FROM products, products_extra_fields, products_to_products_extra_fields 
WHERE products_to_products_extra_fields.products_extra_fields_id = products_extra_fields.products_extra_fields_id AND 
products_to_products_extra_fields.products_id=1 
GROUP BY products_extra_fields.products_extra_fields_id;

+---------------+---------------------------+----------------------------+
| products_name | products_extra_fields_name| products_extra_fields_value|
+---------------+---------------------------+----------------------------+
| product 1     | sugar                     | 20%                        |
| product 1     | cocoa                     | 45%                        |
| product 1     | butter                    | 27%                        |
+---------------+---------------------------+----------------------------+

但我想看看

products_extra_fields_name（牛奶）没有价值

+---------------+---------------------------+----------------------------+
| products_name | products_extra_fields_name| products_extra_fields_value|
+---------------+---------------------------+----------------------------+
| product 1     | sugar                     | 20%                        |
| product 1     | cocoa                     | 45%                        |
| product 1     | butter                    | 27%                        |
| product 1     | milk                      |                            |
+---------------+---------------------------+----------------------------+

对于产品2可可，黄油，牛奶，没有价值只有糖12％

我可以做些什么来获得我想要的结果。

查看我的php脚本（products_edit2.php？id = 1或2）

<?php  
require ('mysql/mysql_connect.php'); // Connect to the database.
        if (is_numeric ($_GET['id']) ) {
    $query = "SELECT 
products_name, products_extra_fields_name, products_extra_fields_value FROM 
products, products_extra_fields, products_to_products_extra_fields WHERE 
products_to_products_extra_fields.products_extra_fields_id = products_extra_fields.products_extra_fields_id AND 
products_to_products_extra_fields.products_id = {$_GET['id']} 
GROUP BY  products_extra_fields.products_extra_fields_id";

if ($result = mysql_query ($query)) {

$query2 = "SELECT products_name FROM products WHERE products_id={$_GET['id']}";
if ($result2 = mysql_query ($query2)) {
$row2 = mysql_fetch_array ($result2);
$products_name = $row2['products_name'];
?>

<form action='products_edit.php' enctype='multipart/form-data' method='POST'>
<table width="50%" border="0" cellpadding="2" cellspacing="2">
<tr>
<td width="20%" align="right">PRODUCTS NAME:</td>
<td><input type="text" name="products_name" size="80" value="<?php echo $products_name; ?>" /></td>
</tr>
<?php 
}
/***** ***** *****/

while ($row = mysql_fetch_assoc ($result)) {
$products_extra_fields_name = $row['products_extra_fields_name'];
$products_extra_fields_value = $row['products_extra_fields_value'];
$products_extra_fields_id = $row['products_extra_fields_id'];
?>
<tr>
<td width="20%" align="right"><?php echo $products_extra_fields_id .'-'. $products_extra_fields_name; ?></td>
<td><input type="text" name="categories_name" size="80" value="<?php echo $products_extra_fields_value; ?>" /></td>
</tr>

<?php }

/***** ***** END *****/
?>
<input type="hidden" name="categories_id" size="10" value="<?php echo $_GET['id']; ?>" />

<tr>
<td width="100%" colspan="2" align="right"><input type="submit" name="submit" value="SAVE"/></td>
</tr>
</table>
</form>

<?php
} else { // Couldn't get the information.
print "<p>Could retrieve the entry because: <b>" . mysql_error() . "</b><br/><br/>. The query was $query.</p>";
}
}else{ // No ID set.
print '<p><b>You must have made a mistake in using this page.</b></p>';
}
?>

</body>
</html>

我想看到所有4个products_extra_fields_name和4个输入框（产品1有3个值1 null，产品2有1个值3 null）

Answer 1

在FROM中使用逗号分隔列表时，MySQL使用内部联接。要得到你想要的东西，你需要使用左连接。

SELECT 
products_name, 
products_extra_fields_name, 
products_extra_fields_value
FROM products, products_extra_fields
LEFT JOIN products_to_products_extra_fields
ON products_to_products_extra_fields.products_extra_fields_id = products_extra_fields.products_extra_fields_id
AND products_to_products_extra_fields.products_id=1 
GROUP BY products_extra_fields.products_extra_fields_id;

这应该产生：

+---------------+---------------------------+----------------------------+
| products_name | products_extra_fields_name| products_extra_fields_value|
+---------------+---------------------------+----------------------------+
| product 1     | sugar                     | 20%                        |
| product 1     | cocoa                     | 45%                        |
| product 1     | butter                    | 27%                        |
| product 1     | milk                      | NULL                       |
+---------------+---------------------------+----------------------------+

mysql查询 - 编辑额外的字段

1 个答案: