如何在两个表中洗牌？

Question

我正在开发 post 系统..
所以，我必须显示用户的朋友和用户参与的组的 posts..
这是我的代码来显示 posts..

<?php
  $sql = "SELECT * FROM posts WHERE uploader_id=:friend_id ORDER BY id DESC";
  $query = $db->prepare($sql);
  $query->execute(array(
     ":friend_id" => $friend_id
  ));
  $rows = $query->fetchAll(PDO::FETCH_ASSOC);
  foreach ($rows as $row) {
      $name = $row['name'];
      echo "POST BY $name";
  }
  $sql = "SELECT * FROM group_posts WHERE id=:member_group ORDER BY id DESC";
  $query = $db->prepare($sql);
  $query->execute(array(
     ":member_group" => $group_id
  ));
  $rows = $query->fetchAll(PDO::FETCH_ASSOC);
  foreach ($rows as $row) {
     $name = $row['name'];
     echo "POST BY $name";
  }
?>

现在，我希望所有这些 post 以 post table 和 group_posts 的所有 post 的方式进行洗牌table按降序显示。

更新

我将我的代码编辑成这个..
我发现首先我必须在编码我的 post 系统之前对此进行编码..

<?php
  $sql = "SELECT * FROM friends WHERE user_one=:me OR user_two=:me2 UNION SELECT * FROM group_members WHERE member_id=:me3";
  $query = $db->prepare($sql);
  $query->execute(array(
      ":me" => $my_id,
      ":me2" => $my_id,
      ":me3" => $my_id
  ));
  $rows = $query->fetchAll(PDO::FETCH_ASSOC);
  foreach ($rows as $row) {
     $user_one = $row['user_one'];
     $user_two = $row['user_two'];
     $group_id = $row['group_id'];
     if ($user_one == $my_id) {
         $friend_id = $user_two;
     } else {
         $friend_id = $user_one;
     }
     echo $friend_id . "<BR>" . $group_id;
  }
?>

现在，问题来了.. 这是成功打印 $friend_id 但是，它在打印 $group_id.
时显示未定义的索引 'group_id' 我检查了所有的字段都是正确的。

Answer 1

尝试仅使用 UNION

的一个查询

SELECT *
FROM (
  SELECT name, id FROM posts WHERE uploader_id=:friend_id
  UNION
  SELECT name, id FROM group_posts WHERE id=:member_group
) p
ORDER BY p.id DESC

请注意，您的内部查询必须 return 相同的 列数，并且顺序相同（我认为也 name/alias 相同） .

如何在两个表中洗牌？

How to shuffle posts in two tables?

php

mysql

pdo