[英]Select Only one result for each user id for a “chat history”
尝试仅返回每个UserId的一个(最新)行(如果包含在MySQL DB中)以使结果显示“聊天记录”。 基本上就像是发送给或来自任何其他用户的最新消息的测试历史记录概述。
<?php
$userId = $_POST['userId'];
$pdo = new PDO('mysql://hostname=localhost;dbname=data_base', 'user', 'password');
$query = $pdo->query("SELECT * FROM `messages` WHERE `from_id`='{$userId}' OR `to_id`='{$userId}' ORDER BY `stamp` DESC");
$data = $query->fetchAll(PDO::FETCH_ASSOC);
echo json_encode($data);
<?php
$userId = $_POST['userId'];
$pdo = new PDO('mysql://hostname=localhost;dbname=data_base', 'user', 'password');
$query = $pdo->query("SELECT * FROM `messages` WHERE `from_id`='{$userId}' OR `to_id`='{$userId}' GROUP BY `from_id`, `to_id` ORDER BY `stamp` DESC");
$data = $query->fetchAll(PDO::FETCH_ASSOC);
echo json_encode($data);
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