Question

我正在尝试输出一个“项目”列表，这些项目都包含“标签”列表。由于标签用于多个项目，我使用的是名为“tag_rel”的桥接表。

$query = mysql_query("SELECT i.*, t.name
                FROM items AS i
                LEFT JOIN tag_rel AS tr ON (tr.item = j.id)
                LEFT JOIN tags AS t ON (t.id = tr.tag)
                ORDER by i.id DESC"); 
while($row = mysql_fetch_array($query)){

我认为这会给我一份我的物品清单。但是如何输出每个项目的给定标签列表？

我知道我不应该对每个查询进行第二次查询，即：

$query = mysql_query("SELECT i.*
                FROM items AS i
                ORDER by i.id DESC L"); 
while($row = mysql_fetch_array($query)){

    $query2 = mysql_query("SELECT t.name
                       FROM tag_rel AS tr
                       LEFT JOIN tags AS t ON (t.id = tr.tag)
                       WHERE tr.item=$row[id]"); 
    while($row2 = mysql_fetch_array($query)){

任何提示？

非常感谢！

Answer 1

试试这个：

SELECT i.*, GROUP_CONCAT(t.name) tagList
FROM items AS i
LEFT JOIN tag_rel AS tr ON (tr.item = j.id)
LEFT JOIN tags AS t ON (t.id = tr.tag)
GROUP BY i.id 
ORDER BY i.id DESC

左连接标记表

1 个答案: