按 Group BY 對多列求和

Question

我的數據庫中有這些數據

Purchase ID: 0012 <br>
Product: 1 <br>
Delivered: 100

Pruchase ID: 0013<br>
Product: 1<br>
Delivered: 10

當我總結相同的產品時，它應該是110但當我使用這個查詢時，總和將是440

SELECT `purchase_orders`.`product`, SUM(purchase_orders.delivered) as system_count, `products`.`code`
FROM `purchase_orders`
JOIN `products` ON `products`.`id` = `purchase_orders`.`product`
WHERE `purchase_orders`.`delivery_status` = 4
GROUP BY `purchase_orders`.`product`

任何人都可以幫助我我的 SQl 有什么問題嗎？

Answer 1

你應該GROUP BY products.code為好。

像下面

SELECT `purchase_orders`.`product`, SUM(purchase_orders.delivered) as system_count, `products`.`code`
FROM `purchase_orders`
JOIN `products` ON `products`.`id` = `purchase_orders`.`product`
WHERE `purchase_orders`.`delivery_status` = 4
GROUP BY `purchase_orders`.`product`, `products`.`code`

Answer 2

select po.Product, sum(po.Delivered) as count from purchase_orders po
group by po.Product