Php 如何从两个以上的表中进行查询

我试着这样做：

    $sql = "SELECT phpbb_users.user_id, phpbb_users.username, phpbb_users.user_colour, topic_poster, phpbb_topics.forum_id, phpbb_forums.forum_price
FROM phpbb_topics LEFT JOIN phpbb_forums ON phpbb_topics.forum_id = phpbb_forums.forum_id
 LEFT JOIN phpbb_users ON phpbb_topics.topic_poster = phpbb_users.user_id WHERE phpbb_users.group_id = '55222'
 OR phpbb_users.group_id = '55229'
 OR phpbb_users.group_id = '55174'
 GROUP BY phpbb_users.user_id ORDER BY phpbb_forums.forum_price DESC";
    $result = $db->sql_query($sql);

while ($row = $db->sql_fetchrow($result))
{

    $template->assign_block_vars('earn', array(
        'USER_ID'                   => $row['user_id'],
        'USERNAME'                  => $row['username'],
        'USER_COLOR'                => $row['user_colour'],
        'U_USER'                    => append_sid($phpbb_root_path . "memberlist." . $phpEx . "?mode=viewprofile&u=" . $row['user_id']),
        'TOTAL_EARN'                => $price,
        'TOTAL_UPLOADS'             => $total_price_singels+$total_price_albums,
        'TOTAL_UPLOADS_LASTMONTH'   => $total_upload_lastmonth,
        'TOTAL_UPLOADS_MONTH'       => $total_upload_month,
    ));
}

这不管用。。。。 我需要查询每个用户，以检查有多少消息，他写了不同的论坛与每个论坛有不同的价格，然后给我的价格，每个用户已获得一般

---

再次感谢。

如果我是对的，你不需要最后一次，在

$total\u upload\u月之后

$sql = "SELECT phpbb_users.user_id, phpbb_users.username, phpbb_users.user_colour, topic_poster, phpbb_topics.forum_id, phpbb_forums.forum_priceFROM phpbb_topics LEFT JOIN phpbb_forums ON phpbb_topics.forum_id = phpbb_forums.forum_id LEFT JOIN phpbb_users ON phpbb_topics.topic_poster = phpbb_users.user_id WHERE phpbb_users.group_id = '55222' OR phpbb_users.group_id = '55229' OR phpbb_users.group_id = '55174' GROUP BY phpbb_users.user_id ORDER BY phpbb_forums.forum_price DESC";
$result = $db->sql_query($sql);
while ($row = $db->sql_fetchrow($result)){
 $template->assign_block_vars('earn', array(        
'USER_ID'                   => $row['user_id'],        
'USERNAME'                  => $row['username'],        
'USER_COLOR'                => $row['user_colour'],        
'U_USER'                    => append_sid($phpbb_root_path . "memberlist." . $phpEx . "?mode=viewprofile&u=" . $row['user_id']),        
'TOTAL_EARN'                => $price,        
'TOTAL_UPLOADS'             => $total_price_singels+$total_price_albums,        
'TOTAL_UPLOADS_LASTMONTH'   => $total_upload_lastmonth,        
'TOTAL_UPLOADS_MONTH'       => $total_upload_month    
));
}

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如果我理解正确，您希望为每个用户计算总和，请尝试以下操作：

---

选择sum（phpbb\u forums.price）作为总金额，

…

您收到的错误消息是什么？怎么会“不工作”呢？我需要知道怎么做。。。我向您展示了我尝试的代码，但它不起作用。在我的代码中，您可以看到我的表和字段。我需要得到每个用户的一般价格，张贴在不同的论坛主题，每个论坛有不同的价格。示例：如果我在两个论坛上发表文章-forum_id1和forum_id2，forum1=1$price，forum2=2$i得到结果3$。。。。很抱歉我的愚蠢的英语