mySQL左連接，右表具有（無行）條件

Question

SHOPS
+----+------------+
| id | shop_name  |
+----+------------+

ORDERBOOKINGS
+-----+---------+-------------+------------+
| id  | shop_id | grand_total | created_at |
+-----+---------+-------------+------------+

我想要一張這樣的桌子：

+------------+--------------+--------------+
| shop_name  | total_orders | total_amount |
+------------+--------------+--------------+

條件是我有日期過濾器，該過濾器僅返回指定日期之間的訂單總數。 我希望它返回所有商店（如果在這些日期之間沒有某些商店的訂單，那么它應該返回那些total_orders為0的商店）。

注意：有些商店甚至可能在訂單表中沒有條目。

我已經嘗試了以下操作，但是它無法從shops表返回所有行：

SELECT COUNT(orderbookings.id),
       SUM(orderbookings.grand_total),
       shops.shop_name
FROM `orderbookings`
LEFT JOIN shops
    on orderbookings.shop_id = shops.id
where orderbookings.created_at BETWEEN "2015-10-22 17:02:02" AND "2017-03-07 17:02:02"
GROUP BY shops.id

知道我該如何實現嗎？

謝謝。

Answer 1

更換where以and您的查詢和LEFT JOIN到RIGHT JOIN ：

SELECT
    COUNT(orderbookings.id),
    COALESCE(SUM(orderbookings.grand_total), 0),
    shops.shop_name 
FROM `orderbookings` 
RIHGT JOIN shops on orderbookings.shop_id = shops.id and orderbookings.created_at BETWEEN "2015-10-22 17:02:02" AND "2017-03-07 17:02:02" 
GROUP BY shops.id

說明：
1）如果要獲得所有商店，則應使用shops作為主表，然后使用左連接orderbookings ，這里我使用右連接，因為您將orderbookings用作主表；
2）如果您在where使用orderbookings的列，則左聯接將作為內部聯接。

最后， left join解決方案將如下所示：

SELECT
    COUNT(orderbookings.id),
    COALESCE(SUM(orderbookings.grand_total), 0),
    shops.shop_name 
FROM `shops ` 
LEFT JOIN orderbookings on orderbookings.shop_id = shops.id and orderbookings.created_at BETWEEN "2015-10-22 17:02:02" AND "2017-03-07 17:02:02" 
GROUP BY shops.id

Answer 2

您想撤消聯接並添加一些IFNULL：

SELECT IFNULL(COUNT(orderbookings.id),0),
       IFNULL(SUM(orderbookings.grand_total),0),
       shops.shop_name
FROM `orderbookings`
RIGHT OUTER JOIN shops
    on orderbookings.shop_id = shops.id
       and orderbookings.created_at BETWEEN "2015-10-22 17:02:02" AND "2017-03-07 17:02:02"
GROUP BY shops.id