Question

我想加入两个表格（sales_flat_order＆amp; sales_flat_order_address）。我想使用一个表中的entity_id与另一个表中的parent_id匹配。现在每entity_id有一行，但每个parent_id有两行。但我只想在加入后有一行。

我正在使用这个Statement但是在连接之后它仍然为每个entity_id返回两行。

select o.customer_email, a.prefix
from sales_flat_order o
left JOIN sales_flat_order_address a on o.entity_id = a.parent_id

有人有想法吗？

Answer 1

只需添加一个不同的？

select DISTINCT o.customer_email, a.prefix
from sales_flat_order o
left JOIN sales_flat_order_address a on o.entity_id = a.parent_id

显然这只会删除多个行，其中o.customer_email，a.prefix实际上是相同的，否则你需要找到一些方法来决定你真正想要的记录......例如：

select o.customer_email, MIN(a.prefix)
from sales_flat_order o
left JOIN sales_flat_order_address a on o.entity_id = a.parent_id
group by o.customer_email

Answer 2

select o.customer_email, 
     a.prefix 
from sales_flat_order o 
 left JOIN (Select  distinct a.prefix, a.parentid 
            from sales_flat_order_address) a
 on o.entity_id = a.parent_id

Answer 3

SELECT  o.customer_email, oa.prefix
FROM    sales_flat_order o
LEFT JOIN
        sales_flat_order_address oa
ON      oa.entity_id =
        (
        SELECT  entity_id
        FROM    sales_flat_order_address oai
        WHERE   oai.parent_id = o.entity_id
        ORDER BY
                FIND_IN_SET(address_type, 'billing,shipping')
        LIMIT 1
        )

通过这种方式，您将从帐单邮寄地址（如果已设置）获取前缀，如果未设置帐单邮寄地址，则会返回到送货地址。

SQL连接表（a，b） - 但只包含来自a的行

3 个答案: