SQL从表总和中选择ID并按ID分组

Question

我需要一些小帮助来分组和汇总项目ID的数量。

来自数据库的数据：

products
id  code    name            price
1   1234    Product name    12
2   1235    Product name    12
3   1236    Product name    12

warehouses_products
product_id   warehouse_id   quantity
1           1               12
2           1               0
2           2               3
3           1               1
3           2               1

PHP获取数据。

$db = new PDO('mysql:host=localhost;dbname=data2;charset=utf8', 'user2', 'Password');

foreach($db->query('SELECT * FROM products as pr INNER JOIN warehouses_products AS s ON (s.product_id = pr.id) group by pr.id') as $row) {
echo $row["code"] . ' ' . $row["quantity"];
}

一个例子：如果我在2个仓库中有相同的代码，这只会得到其中1个仓库，我想要的是对产品的数量和组乘以product_id。

任何帮助表示赞赏。

Answer 1

尝试这个 ：

'SELECT *, SUM(s.quantity) AS sum_quantity FROM products as pr INNER JOIN warehouses_products AS s ON (s.product_id = pr.id) group by pr.id'

在你的foreach ：

echo $row["code"] . ' ' . $row["sum_quantity"];

Answer 2

查询：

SELECT p.id, p.code, SUM(wp.quantity) as quantity
FROM products p
JOIN warehouses_products wp ON wp.product_id = p.id
GROUP BY p.id, p.code

PHP：

$db = new PDO('mysql:host=localhost;dbname=data2;charset=utf8', 'user2', 'Password');

foreach($db->query('SELECT p.id, p.code, SUM(wp.quantity) as quantity FROM products p JOIN warehouses_products wp ON wp.product_id = p.id GROUP BY p.id, p.code') as $row) {
echo $row["code"] . ' ' . $row["quantity"];
}

切记，我们所依赖的事实是产品表中的代码和ID是唯一的对。