Question

My tables

    $sql="SELECT *
          FROM addresses
          LEFT JOIN users ON address_id = user_id
          LEFT JOIN notes ON note_id = user_id
          ORDER BY id DESC
          LIMIT 1";

这是我的SQL查询，我的任务是显示3个表中的最后一条记录，但表格是空白的，我不知道为什么，提前感谢人们:)

Answer 1

我猜问题来自 ORDER BY id DESC 。实际上，你没有所谓的id列。您应该删除此子句，以使代码正常工作。

如果你想取最后的记录，你可以放一个 ORDER BY address_id DESC 来完成这项工作！

直接编辑的代码：

      $sql="SELECT *
      FROM addresses
      LEFT JOIN users ON address_id = user_id
      LEFT JOIN notes ON note_id = user_id
      ORDER BY adress_id DESC
      LIMIT 1";

Answer 2

这可能有效：

SELECT a.address_id, u.user_id, n.note_id
FROM addresses a
LEFT JOIN users_addresses ua ON ua.ua_address_id = a.address_id
LEFT JOIN users u ON u.user_id = ua.ua_user_id
LEFT JOIN notes n ON n.note_user_id = u.user_id
ORDER BY a.address_id DESC
LIMIT 1

Answer 3

这是从所有表中获取所有数据的查询，不确定你的意思是3个表的最后记录是什么，我可以在那里看到四个表：

SELECT *
FROM `addresses`
LEFT JOIN `users_addresses` ON `users_addresses`.`ua_address_id` = `addresses`.`address_id`
LEFT JOIN `users` ON `users`.`user_id` = `users_addresses`.`ua_user_id`
LEFT JOIN `notes` ON `notes`.`note_user_id` = `users`.`user_id`;

从3个表中获取最后的记录

3 个答案: