Mysql DISTINCT 和 COUNT 查询

Question

我在获取查询输出我想要的方式时遇到问题，

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'

正在返回结果：

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

但我希望它能带回 distinct item_id 并将数量加在一起，但是当我尝试添加 distinct 并计数时，我最终只返回了一行。

Answer 1

如果您想要对相同项目的数量求和，请尝试分组而不是 item_id。像这样：

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

请使用group by子句

 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`;

Mysql DISTINCT 和 COUNT 查询

Mysql DISTINCT and COUNT query

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count

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