Question

我有这个问题：

    SELECT users.username, users.profile_img, m.address, m.id
    FROM friend f 
    INNER JOIN users ON f.user_acc = users.username
    INNER JOIN maps m ON users.username = m.username
    WHERE (f.user_req = 'john' AND f.status = 1) 

    UNION DISTINCT 

    SELECT users.username, users.profile_img, m.address, m.id
    FROM friend f 
    INNER JOIN users ON f.user_req = users.username
    INNER JOIN maps m ON users.username = m.username
    WHERE (f.user_acc = 'john' AND f.status = 1) 

    ORDER BY id DESC

当我从phpmyadmin手动运行时，此查询有效。但是，当我从PHP代码运行它不再有效。我用这种方式改造它：

    $stmt = $db->prepare("SELECT `users.username`, `users.profile_img`, `m.address`, `m.id`
               FROM `friend` `f` 
               INNER JOIN `users` ON `f.user_acc` = `users.username`
               INNER JOIN `maps` `m` ON `users.username` = `m.username`
               WHERE (`f.user_req` = '".$username."' AND `f.status` = '1') 
                  UNION DISTINCT 
               SELECT `users.username`, `users.profile_img`, `m.address`, `m.id`
               FROM `friend` `f` 
               INNER JOIN `users` ON `f.user_req` = `users.username`
               INNER JOIN `maps` `m` ON `users.username` = `m.username`
               WHERE (`f.user_acc` = '".$username."' AND `f.status` = '1') 
                  ORDER BY `id` DESC");

$ username替换'john'。错误在哪里？我认为报价是正确的.. 谢谢！

查询报价不起作用

0 个答案: