在mysql中使用内连接和concat（）操作进行查询

Question

我有两张桌子：

sk_accounts      //details of user

• acnt_user_id
• acnt_fname //名字
• acnt_lname
• acnt_profile_picture
• acnt_member_class

• 等........

   sk_following   //table containing details of users who are following others
  

• ID

• flwing_follower_id //被其他关注者关注的用户的ID
• flwing_following_user_id

• following_date

  我想根据以下Mysql代码显示关注者的详细信息。不幸的是，虽然有3行，但它返回零行。我的查询是这样的：

  $query_following = "SELECT sk_following.flwing_following_user_id, 
  sk_accounts.acnt_fname,
  sk_accounts.acnt_lname,
  sk_accounts.acnt_member_class,
  sk_accounts.acnt_profile_picture
  FROM sk_following 
  INNER JOIN sk_accounts 
  WHERE sk_following.flwing_follower_id='$id' AND        sk_accounts.acnt_user_id=sk_following.flwing_following_user_id AND CONCAT(sk_accounts.acnt_fname,' ',sk_accounts.acnt_lname)='$name'";
  $result_following = mysql_query($query_following);
  $count_following = mysql_num_rows($result_following);
  echo $count_following;
  

注意：$ id和$ name包含值 请帮助我。谢谢。

Answer 1

试试这个，

"SELECT sk_following.flwing_following_user_id,
sk_accounts.acnt_fname,
sk_accounts.acnt_lname,
sk_accounts.acnt_member_class,
sk_accounts.acnt_profile_picture 
FROM sk_following
LEFT JOIN sk_accounts ON sk_accounts.acnt_user_id=sk_following.flwing_following_user_id
WHERE sk_following.flwing_follower_id='$id'
AND CONCAT(sk_accounts.acnt_fname,' ',sk_accounts.acnt_lname)='$name'";

这可能对你有所帮助。

Answer 2

如果没有看到样本数据和所需的输出，很难完全理解，但是你的JOIN应该在flwing_follower_id而不是flwing_following_user_id吗？

SELECT sk_following.flwing_following_user_id,
    sk_accounts.acnt_fname,
    sk_accounts.acnt_lname,
    sk_accounts.acnt_member_class,
    sk_accounts.acnt_profile_picture 
FROM sk_following 
    INNER JOIN sk_accounts ON sk_accounts.acnt_user_id=sk_following.flwing_follower_id 
WHERE sk_following.flwing_follower_id='$id' 
    AND CONCAT(sk_accounts.acnt_fname,' ',sk_accounts.acnt_lname)='$name'

祝你好运。