Question

我有以下代码（你不需要知道很多查询来得到我的问题）：

if ($stmt = $cxn->prepare('SELECT p.post_id, p.reply_to, p.parent_id, p.post_path, p.user_id, p.content, p.datetime, p.total_likes, p.total_replies, p.total_reposts, l.like_id, l.user_id, u.username, u.display_name 
        FROM posts p 
        LEFT JOIN users u ON p.user_id = u.user_id 
        LEFT JOIN likes l ON l.post_id = p.post_id 
        WHERE l.user_id IN 
            (SELECT user_id FROM likes WHERE user_id IN 
                (SELECT following_id FROM follows WHERE user_id = ? AND following_id != ?)) 
        AND l.user_id != p.user_id AND p.removed != 1 
        ORDER BY p.datetime DESC LIMIT 26')) {
    $stmt->bind_param('ii', $id, $id);
    $stmt->execute();
    $stmt->store_result();
    $stmt->bind_result($post_id, $reply_to, $parent_id, $post_path, $user_id, $content, $datetime, $total_likes, $total_replies, $total_reposts, $like_id, $like_user_id, $username, $display_name);
}

现在，我有l.user_id值，即用户的整数值。

如果我已经l.user_id查询了users，我将如何添加到此查询以便从u.username表中获取p.user_id的用户名？< / p>

谢谢！

Answer 1

您可以使用别名来实现此目的，它们可以在您的情况下使用，例如

SELECT l.user_name as user, u.username as uname, ....

来自文档

SQL别名

SQL别名用于为数据库表或表中的列提供临时名称。



基本上创建了别名以使列名更具可读性。

了解详情here

Answer 2

试试这个

   if ($stmt = $cxn->prepare('SELECT p.post_id, p.reply_to, p.parent_id, p.post_path, p.user_id, p.content, p.datetime, p.total_likes, p.total_replies, p.total_reposts, l.like_id, l.user_id, l.username as lusername , u.username, u.display_name 
    FROM posts p
    ....

编辑：

更改此

LEFT JOIN likes l ON l.post_id = p.post_id

到

LEFT JOIN likes l ON l.post_id = p.post_id AND l.user_id= u.user_id

获取相同的列两次，不同的值

2 个答案: