连接两个表以匹配整数以获取用户名

Question

我无法弄清楚如何连接两个表和 SELECT 来自不同数据库表的不同行。

我想添加我的users 表以匹配id 和post_creator，然后从users 表中获取username，只要id 和post_creator 号码匹配。

因此，如果我的 users 表的 id 为 10，那就是 Jim 的用户名。如果 post_creator 值为 10，我希望 Jim 被找到并回显。

现在这正在杀死代码，我不知道我做错了什么。

while ($row = $stmt->fetch()) {
        //added in topic title variable
        $topic_title;
//  foreach($stmt as $row) {
        //Prepared SELECT stmt to get forum posts
        $stmt2 = $con->prepare("SELECT forum_posts.id, forum_posts.category_id, forum_posts.topic_id, forum_posts.post_creator, forum_posts.post_content, forum_posts.post_date users.id
        FROM forum_posts LEFT JOIN users WHERE forum_posts.category_id=? AND forum_posts.topic_id=? AND forum_posts.post_creator=? AND users.id=?");
        if($stmt2===false) {
            die();
        } else {
        //var_dump($stmt2);

            $stmt2->bind_param("ii", $cid, $tid);
            $stmt2->execute();
            $stmt2->store_result();
            $stmt2->bind_result($post_id, $post_category_id, $post_topic_id, $post_creator, $post_content, $post_date);
            if (!$stmt2) {
            throw new Exception($con->error);
            }
        }
    $num_rows2 = $stmt2->num_rows;
    if($num_rows2) {
        $count2=0;
        while($stmt2->fetch()) {
        $count2++;
        $post_id;
        $post_category_id;
        $post_topic_id;
        $post_creator;
        $post_content;
         $post_date = fixDate($post_date);
        //$post_date;
            echo "<tr><td valign='top' style='border: 1px solid #000000;'>
            <div style='min-height: 125px;'>".$topic_title. "Post ".$count2."<br />
            by ".$post_creator." - " .$post_date. "<hr />" . $post_content ."</div></td>
            <td width='200' valign='top' align='center' style='border: 1px solid #000000;'>User Info Here!</td></tr>
            <tr><td colspan='2'><hr /></td></tr>";
        }

Answer 1

你可以加入表格...比如这个（加入用户、类别和主题）

SELECT forum_posts.id post_id, forum_posts.category_id post_category_id, forum_posts.topic_id post_topic_id, forum_posts.post_creator, forum_posts.post_content, forum_posts.post_date, forum_post_categories.category_name, forum_post_topics.topic_name, users.id user_id, users.username user_username FROM forum_posts LEFT JOIN users ON users.id = forum_posts.post_creator RIGHT JOIN forum_post_categories ON forum_post_categories.id = forum_posts.category_id RIGHT JOIN forum_post_topics ON forum_post_topics.id = forum_posts.topic_id WHERE forum_posts.category_id=? AND forum_posts.topic_id=? AND forum_posts.post_creator=? AND users.id=?

注意：这是未经测试的。

Answer 2

select u.*,fp.*  from users u inner join forum_posts fp u.id=fp.post_creator
where  fp.category_id=? AND fp.topic_id=? AND fp.post_creator=? AND  u.id=?

更新查询：

select u.user_name,fp.post_creator from 
users u inner join forum_posts fp u.id=fp.post_creator

检查这个更新的，它只会给你 user_name 和 post_creator

Answer 3

尝试删除此代码部分

        if($stmt2===false) {
            die();
        } else {  }

简单地做：

 $stmt2 = $con->prepare("SELECT forum_posts.id, forum_posts.category_id, forum_posts.topic_id, forum_posts.post_creator, forum_posts.post_content, forum_posts.post_date users.id
        FROM forum_posts LEFT JOIN users WHERE forum_posts.category_id=? AND forum_posts.topic_id=? AND forum_posts.post_creator=? AND users.id=?");
$stmt2->bind_param("ii", $cid, $tid);
            $stmt2->execute();
            $stmt2->store_result();
            $stmt2->bind_result($post_id, $post_category_id, $post_topic_id, $post_creator, $post_content, $post_date);
            if (!$stmt2) {
            throw new Exception($con->error);
            }