Question

考虑下面的SQL查询：

SELECT DISTINCT shops.*, 
       DA.delivery_cost, 
       DA.postcode 
FROM shops 
       JOIN shops_delivery_area as DA on DA.shop_id = shops.id 
WHERE DA.postcode = "Liverpool" 
      OR location = "Liverpool"

shops表

+----+----------+-----------+----------+
| id | name     | location  | postcode |
+----+----------+-----------+----------+
|  1 | Shop One | Liverpool | L10      |
|  2 | Shop Two | Liverpool | L16      |
+----+----------+-----------+----------+

shops_delivery_area表

+------------------+---------+----------+---------------+
| delivery_area_id | shop_id | postcode | delivery_cost |
+------------------+---------+----------+---------------+
|                1 |       1 | L10      |          0.00 |
|                2 |       1 | L11      |          0.00 |
|                3 |       1 | L12      |          1.00 |
|                4 |       1 | L13      |          1.00 |
|                5 |       2 | L10      |          0.00 |
|                6 |       2 | L16      |          0.00 |
|                7 |       2 | L28      |          0.00 |
+------------------+---------+----------+---------------+

用户可以通过邮政编码（例如：L14，L15，L16）或文本框中的位置进行搜索。

如果用户输入“利物浦”，它将找到位于“利物浦”的所有商店。问题是会有重复的商店名称（商店表）。如何解决这个问题？

结果（按位置搜索）：

如何避免重复商店名称？

我应该这样做：shops.id = shops_delivery_area.shop_id AND shops.postcode = shops_delivery_area.postcode

+----+----------+-----------+----------+---------------+----------+
| id | name     | location  | postcode | delivery_cost | postcode |
+----+----------+-----------+----------+---------------+----------+
|  1 | Shop One | Liverpool | L10      |          0.00 | L10      |
|  1 | Shop One | Liverpool | L10      |          0.00 | L11      |
|  1 | Shop One | Liverpool | L10      |          1.00 | L12      |
|  1 | Shop One | Liverpool | L10      |          1.00 | L13      |
|  2 | Shop Two | Liverpool | L16      |          0.00 | L10      |
|  2 | Shop Two | Liverpool | L16      |          0.00 | L16      |
|  2 | Shop Two | Liverpool | L16      |          0.00 | L28      |
+----+----------+-----------+----------+---------------+----------+

结果（按邮政编码L10搜索）： 按预期正常工作

+----+----------+-----------+----------+---------------+----------+
| id | name     | location  | postcode | delivery_cost | postcode |
+----+----------+-----------+----------+---------------+----------+
|  1 | Shop One | Liverpool | L10      |          0.00 | L10      |
|  2 | Shop Two | Liverpool | L16      |          0.00 | L10      |
+----+----------+-----------+----------+---------------+----------+

Answer 1

在“按位置排列的结果”中，您有“delivery_cost”和“postcode”，只要它们不同，您将始终获得“重复”删除这两个，并且您只会看到其中一个。

编辑：如果您需要这些字段以及商店应该具有的默认值。如果您需要“delivery_cost”和“postcode”的所有结果，但只有一个结果，您应该重新考虑您正在尝试做什么或解释您期望的结果。

Answer 2

SELECT shops.*, 
MIN(DA.delivery_cost), 
MIN(DA.postcode) 
FROM shops 
JOIN shops_delivery_area as DA on 
       (DA.shop_id = shops.id AND shops.postcode = DA.postcode)
WHERE DA.postcode = "Liverpool" 
      OR location = "Liverpool"
GROUP BY shops.location, shops.name, shops.id, shops.postcode

Answer 3

匹配两个表中的邮政编码，在按位置搜索时会为您提供不同的商店名称。

之类的东西

SELECT DISTINCT shops.*, 
       DA.delivery_cost, 
       DA.postcode 
FROM shops 
       JOIN shops_delivery_area as DA on (DA.shop_id = shops.id  and DA.postcode = shops.postcode)
WHERE DA.postcode = "Liverpool" 
      OR location = "Liverpool"

Answer 4

我设法让它运转起来。我用UNION来解决这个问题。

SELECT U.* FROM 
   ((SELECT DISTINCT shops.*, DA.delivery_cost, DA.postcode AS AreaPostcode FROM shops
             JOIN shops_delivery_area2 as DA on DA.shop_id = shops.id
   WHERE DA.postcode = "Liverpool")
  UNION
   (SELECT DISTINCT shops.*, DA.delivery_cost, DA.postcode AS AreaPostcode FROM shops
             JOIN shops_delivery_area2 as DA on DA.shop_id = shops.id AND DA.postcode = shops.postcode
   WHERE shops.location = "Liverpool")) as U

如果无论如何要缩短或改进此代码，请告诉我。感谢

重复问题

4 个答案: