Question

我有以下可能与此查询相关的MySQL表：

Table: user_follow
Columns:   |  Type:
-----------|---------
id         |  INT(11)
follower   |  INT(11)
user       |  INT(11)
subscribed |  INT(11)

ID是跟随者的ID，跟随者是关注用户的人，订阅者是跟随他们的人。关注者和用户将是用户表中人员的ID：

Table: users
Columns:  |  Type:
----------|---------
id        |  INT(11)
username  |  INT(11)

这不是完整的用户表，但对于MySQL查询所做的任何事情都应该足够了。 users表中的ID是用户的ID，用户名是用户名。所以这是我试图弄清楚它在做什么的查询。我相信它正试图从用户的数据库中获取用户名：

SELECT `ufollower`.`id` AS follower_id, `ufollower`.`username` AS follower_name,
     `ufollowed`.`id` AS user_id, `ufollowed`.`username` AS user_name
FROM `user_follow`
JOIN users ufollower ON `ufollower`.`id` = `user_follow`.`follower`
JOIN users ufollowed ON `ufollowed`.`id` = `user_follow`.`user`
WHERE `user_follow`.`user` = :p_id

我尝试运行的完整代码是这个（包括查询）：

//Get people who this person is following
$following = $db->prepare("SELECT `ufollower`.`id` AS follower_id, `ufollower`.`username` AS follower_name, `ufollowed`.`id` AS user_id, `ufollowed`.`username` AS user_name FROM `user_follow` JOIN users ufollower ON `ufollower`.`id` = `user_follow`.`follower` JOIN users ufollowed ON `ufollowed`.`id` = `user_follow`.`user` WHERE `user_follow`.`user` = :p_id");
$following->bindValue(":p_id",$p_id,PDO::PARAM_STR);
$following->execute();
$following = $following->fetchAll(PDO::FETCH_ASSOC);
var_dump($following);

//If I do $following = $following->fetch(); and var_dump that, it returns "bool(false)" which I learned the other day that it couldn't do the query or there were no results found or something

另外，我不是MySQL的专家，所以如果你能提供一个可行的答案，那就太好了。我可以做简单的查询，但是当谈到加入表时，我不知道发生了什么。

Answer 1

基本上，user_follow表连接另外两个用户，一个跟随另一个用户，此查询为一个特定的跟随者获取这两个用户。

解释的这个问题可以描述为：
对于id为id的user_follow，获取一个跟随另一个用户（ufollowing）的用户（ufollower）及其id和用户名。

试图找出MySQL查询的作用（不是我的）

1 个答案: