自联接仅返回一条记录

Question

在库存管理系统上工作，我们有以下表格：

================================================
| orders | order_line_items  | product_options | 
|--------|-------------------|-----------------|
| id     | id                | id              |
| start  | order_id          | name            |
| end    | product_option_id |                 |
|        | quantity          |                 |
|        | price             |                 |
|        | event_start       |                 |
|        | event_end         |                 |
================================================

我试图来计算某一特定日期的库存，所以我需要做自连接到order_line_items 数量在order_line_items与同product_option_id比较其他记录的数量的总和，并在事件开始和结束在一定范围内。

那么，鉴于2016-01-20的日期，我有：

SELECT order_line_items.id, order_line_items.product_option_id, order_line_items.order_id FROM order_line_items
WHERE order_line_items.event_end_date >= '2016-01-20 04:00:00'
AND order_line_items.event_start_date <= '2016-01-21 04:00:00'
AND order_line_items.product_option_id IS NOT NULL;

以上返回127行

当我尝试自我加入时，如下：

SELECT 
order_line_items.id, 
order_line_items.product_option_id, 
order_line_items.order_id, 
order_line_items.quantity, 

other_line_items.other_product_option_id, 
other_line_items.other_order_id, 
other_line_items.other_quantity, 
other_line_items.total 

FROM order_line_items

JOIN (
    SELECT 
        id, 
        product_option_id AS other_product_option_id, 
        order_id AS other_order_id, 
        quantity AS other_quantity, 
        SUM(quantity) total
    FROM order_line_items
    WHERE order_line_items.event_end_date >= '2016-01-20 04:00:00'
    AND order_line_items.event_start_date <= '2016-01-21 04:00:00'
) other_line_items ON order_line_items.product_option_id = other_line_items.other_product_option_id

WHERE order_line_items.event_end_date >= '2016-01-20 04:00:00'
AND order_line_items.event_start_date <= '2016-01-21 04:00:00'
AND order_line_items.product_option_id IS NOT NULL;

它只返回1条记录。 正如你在这里看到的那样：（ https://goo.gl/BhUYxK ）有很多记录使用相同的product_option_id，所以这最后一个查询应该返回很多行

Answer 1

添加的SUM(...)将子查询转换为单行。 也许子查询需要其中一个：

GROUP BY (id)
GROUP BY (product_option_id)
GROUP BY (order_id)

（我不清楚架构或应用程序是否足以说出哪些有意义。）

（请使用更短，更独特的别名;由于order_line_items和other_line_items的长度和相似性，SQL很难阅读。）

Answer 2

你真的想要得到以下内容吗？ ：

SELECT product_option_id, sum(quantity)
FROM order_line_items
WHERE event_end_date   >= '2016-01-20 04:00:00'
AND   event_start_date <= '2016-01-21 04:00:00'
GROUP BY 1

我不知道为什么你需要在这里自我加入

Answer 3

如果没有样本结果，很难说出你想要的东西，但这会让你比较每个订单的产品选项的数量与范围内的总数：

SELECT oli.order_id, 
       oli.product_option_id,
       oli.quantity,
       po.total_quantity   
  FROM order_line_items oli
  JOIN (
    SELECT product_option_id,
           SUM(quantity) total_quantity
      FROM order_line_items
     WHERE event_end   >= '2016-01-20 04:00:00'
       AND event_start <= '2016-01-21 04:00:00'
  GROUP BY product_option_id
       ) po
    ON po.product_option_id = oli.product_option_id
 WHERE oli.event_end   >= '2016-01-20 04:00:00'
   AND oli.event_start <= '2016-01-21 04:00:00'

如果您可以在订单中拥有相同product_option的多行，则可能需要对其进行调整：

  SELECT oli.order_id, 
         oli.product_option_id,
         SUM(oli.quantity) order_quantity,
         po.total_quantity   
    FROM order_line_items oli
    JOIN (
      SELECT product_option_id,
             SUM(quantity) total_quantity
        FROM order_line_items
       WHERE event_end   >= '2016-01-20 04:00:00'
         AND event_start <= '2016-01-21 04:00:00'
    GROUP BY product_option_id
         ) po
      ON po.product_option_id = oli.product_option_id
   WHERE oli.event_end   >= '2016-01-20 04:00:00'
     AND oli.event_start <= '2016-01-21 04:00:00'
GROUP BY oli.order_id, 
         oli.product_option_id

Answer 4

根据我的理解，您实际上应该将orders和product_options加入order_line_items表。

对于特定日期之间订单上的商品数量，您的查询应如下所示。

SELECT product_options.id, production_options.name, SUM(order_line_items.quantity)
FROM order_line_items
LEFT JOIN product_options ON production_options.id=order_line_items.product_option_id
LEFT JOIN orders ON orders.id=order_line_items.order_id
WHERE orders.start>='SOME DATETIME' AND orders.end<='SOME DATETIME'
GROUP BY product_options.id

另外，只是评论， product_options应该只是命名products 。 胜利的表名更短！