php - Mysql - PHP - 查看总和列

Question

我如何查看 (Collections) 列的总和，其中 (userid = $userid)？

示例:我需要查看用户 id = 2，集合 = 200 + 330 = 530 的结果，我需要查看此结果 (530)

我的 table

------------------------------
| id | user_id | Collections |
------------------------------
| 1  |    2    |     200     |
------------------------------
| 2  |    2    |     330     |
------------------------------
| 3  |    7    |     120     |
------------------------------
| 4  |    8    |     760     |
------------------------------
| 5  |    9    |     200     |
------------------------------
| 6  |    9    |     100     |
------------------------------

我的代码

<?php

$user_id = get_current_user_id();

$servername = "localhost";
$username = "root";
$password = "root";
$dbname = "dbname";

// Create connection
$conn = new mysqli($servername, $username, $password, $dbname);

// Check connection
if ($conn->connect_error) {
    die("Connection failed: " . $conn->connect_error);
} 

$query = "SELECT SUM(Collections) FROM invoices where user_id = $user_id"; 

$result = mysql_query($query) or die(mysql_error());



// Print out result

?>

• 我是 php 和 mysql 的初学者

Answer 1

你可以试试这个:

SELECT SUM(i.Collections) AS totalCollection
FROM invoices AS i
WHERE i.user_id = '$user_id'
GROUP BY i.user_id