自連接只返回一個記錄

Question

上的庫存管理系統的工作，我們有如下表：

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

我試圖來計算某一特定日期的庫存，所以我需要一個自聯接將order_line_items上的數量與具有相同product_option_id的order_line_items中的其他記錄數量的SUM進行比較，以及事件開始和結束在某個範圍內的位置。

所以，對於一個日期2016年1月20日，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; 

以上的回報127行

當我嘗試做一個自我加入，就像這樣：

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條記錄。正如你在這裏看到的：（）有相同的product_option_id有很多記錄，所以這最後一個查詢應該返回很多行

Answer 1

添加SUM(...)將子查詢變成一行。也許，子查詢需要有其中之一：（我不知道該架構或應用不夠好，說這是有道理的）

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

（請用更短，更鮮明，別名;由於order_line_items和other_line_items的長度和相似性，SQL非常難以閱讀。）

Answer 2

您是否確實想要獲得以下內容？ ：

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 

我不能告訴你爲什麼需要一個自我在這裏加入

Answer 3

很難告訴你想要什麼沒有樣品的結果，但是這會給你的每一個訂單的產品選項數量的比較該範圍內的總：

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' 

如果你能有一個順序的相同product_option的多行，你可能需要調整這個像這樣：

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

根據我的理解，您應該將orders和product_options加入到order_line_items表中。

您的查詢應該看起來像這樣，對於特定日期之間的訂單上的項目數量。

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 

而且，只是一個評論，product_options應可能只是被命名爲products。贏得更短的表名稱！