如何更新最終關聯記錄

我有items列表屬於orders。每個item都有fee_percentage字段。並且items的總和是total_price在orders表中。如何更新最終關聯記錄

我想實現什麼？我想更新上次關聯項目的fee字段。

_________________________  __________________________________________ 
| order ID | total_price|  | id | order_id | fee_percentage | fee | 
-------------------------  ------------------------------------------ 
| 334 |  425 |  | 1 | 334 |  50  | 212 | 
    # The `fee` should be 213 => | 2 | 334 |  50  | 212 |

正如你所看到的items總和將是424我想剩下的費用添加到最後一個項目fee。（所以物品id 2的費用應該是213）。

請幫忙嗎？

這是我寫到目前爲止

UPDATE items AS i 
LEFT JOIN orders AS o ON o.order_id = b.order_id 
LEFT JOIN (
    SELECT order_id, SUM(fee) AS sum_fee 
    FROM items 
    GROUP BY order_id 
    WHERE deleted = 0 
) AS b1 ON b1.order_id = b.order_id 
SET b.fee = b.fee + (o.total_price - b1.sum_fee) 
WHERE b.deleted = 0;

我試圖將其附加先前查詢或更新的訂單記錄last_item_id，但它不工作。

LEFT JOIN (
    SELECT order_id, MAX(id) AS b_last_item_id 
    FROM items 
    WHERE deleted = 0 
    GROUP BY order_id  
) AS b1 ON b1.order_id = b.order_id

來源

2017-01-17 Fury

請參閱http://meta.stackoverflow.com/questions/333952/why-should-i-provide-an-mcve-for-what-seems-to-me-to-be-a-very -simple-sql-query – Strawberry

UPDATE items AS b 
    JOIN (
     SELECT MAX(i.id) mid, o.curr_price - SUM(i.fee) AS diff 
     FROM items AS i 
     INNER JOIN orders AS o ON i.order_id = o.order_id 
     GROUP BY i.order_id 
     ORDER BY i.order_id, i.id 
    ) AS v ON b.id = v.mid 
    SET b.fee = b.fee + v.diff WHERE v.diff <> 0;

來源

2017-01-17 15:24:00 Fury

它似乎也起作用。 –

快得多，準確。 – Fury

這有點棘手。我認爲以下查詢應該工作：

UPDATE items AS i 
JOIN orders AS o ON i.order_id = o.orderID 
JOIN (
    SELECT order_id, SUM(fee) AS sum_of_fees 
    FROM items 
    GROUP BY order_id 
) AS i2 ON i2.order_id = o.orderID 
LEFT JOIN items AS i3 
    ON i3.order_id = o.orderID AND i3.id > i.id 
SET i.fee = o.total_price - (sum_of_fees - i.fee) 
WHERE i3.id IS NULL;

使用的派生表計算每order_id費的總和。使用這個值，我們可以計算出所有項目的總和而是作爲當前項：需要以識別具有最大id值，這是記錄在記錄

SUM(fee) - i.fee

另外一個LEFT JOIN到items表實際上正在更新。

來源

2017-01-17 14:46:50

如何更新最終關聯記錄

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