是否可以将这两个SQL语句合并为一个？

Question

我正在使用这两个MySQL语句来获取两个用户之间的所有消息，但是稍后在代码中处理数据时遇到了一个很大的问题，因为它不是按ID顺序排列的。 有什么方法可以组合这些语句并按ID排序结果？

$sql = "SELECT * FROM messages WHERE sender='" . $username . "' AND receiver='" . $chatPartner . "'"

$sqlTwo = "SELECT * FROM messages WHERE sender='" . $chatPartner . "' AND receiver='" . $username . "'"

从本质上讲，我需要两个人之间每次出现一条消息，但都按ID排序。 截至目前，我正在加入数组以获取我的完整列表，但这并不是按ID排序。

Answer 1

SELECT * FROM messages 
WHERE (sender='" . $username . "' AND receiver='" . $chatPartner . "'")
OR (sender='" . $chatPartner . "' AND receiver='" . $username . "'")
ORDER BY id DESC

Answer 2

将两者合并为1个查询怎么样？

$sql = "SELECT * FROM messages WHERE (sender=" . $username . " OR sender =". $chatPartner .") AND (receiver=" . $chatPartner . " OR receiver=" . $username .") ORDER BY id"

Answer 3

您还可以使用行构造函数编写@dtj答案的较短版本。

SELECT *
FROM messages
WHERE (sender, receiver) IN (($username, $chatPartner),($chatPartner, $username))
ORDER BY id DESC

在我看来，它在代码中看起来更好一些，并使其更具可读性，但是请记住，它并不能提高执行性能。