MySQL DISTINCT和COUNT查詢

Question

即時通訊在獲取查詢以輸出我想要的方式時遇到問題，

SELECT 
    `orders`.`item_id`, 
    `products`.`item_code`, 
    `products`.`item_name`, 
    `orders`.`quantity` 
FROM 
    `orders` 
    JOIN `products` ON `orders`.`item_id` = `products`.`id` 
    JOIN `suppliers` ON `products`.`supplier_ref` = `suppliers`.`supplier_ref` 
WHERE 
    `suppliers`.`id` = 159 
    AND `orders`.`order_status` = 'NOTED'

返回結果：

item_id item_code item_name            quantity
1271    RA001G    Green Mop Bucket 12L 2
1270    RA001     Blue Mop Bucket 12L  1
1270    RA001     Blue Mop Bucket 12L  1

但是我希望它帶回與眾不同的item_id，並且當我嘗試添加與眾不同並計數時，最終我只返回了一行。

Answer 1

如果要匯總相同項目的數量，請嘗試對item_id進行分組 。 像這樣：

SELECT 
    `orders`.`item_id`, 
    `products`.`item_code`, 
    `products`.`item_name`, 
    sum(`orders`.`quantity`) as quantity, 
FROM 
    `orders` 
    JOIN `products` ON `orders`.`item_id` = `products`.`id` 
    JOIN `suppliers` ON `products`.`supplier_ref` = `suppliers`.`supplier_ref` 
WHERE 
    `suppliers`.`id` = 159 
     AND `orders`.`order_status` = 'NOTED'
  GROUP BY `orders`.`item_id`, 
      `products`.`item_code`, 
      `products`.`item_name`

Answer 2

請使用分組方式

 SELECT 
`orders`.`item_id`, 
`products`.`item_code`, 
`products`.`item_name`, 
 sum(`orders`.`quantity`) as quantity
 FROM 
  `orders` 
   JOIN `products` ON `orders`.`item_id` = `products`.`id` 
   JOIN `suppliers` ON `products`.`supplier_ref` =   `suppliers`.`supplier_ref` 
WHERE 
 `suppliers`.`id` = 159 AND `orders`.`order_status` = 'NOTED'
group by 
 `orders`.`item_id`;