Question

两个表：人和地址; join condition是addresses.key_value = person.person_id。

有三个地址.address_type：'R'，'M'，'T'。

获取person.first_name，addresses.address_1，addresses.zip，addresses.state

如果address_type'T'然后获取'T'的地址，否则如果'M'，则'R'。

对于每个地址，地址表中都有唯一的address_id。

Answer 1

如果您使用sqlserver 2005+，这可能是您的解决方案：

select * from person p
--cross apply instead of outer apply if you only want people with addresses
outer apply
(select top 1 with ties * from addresses where p.person_id = key_value
order by case address_type when 'T' then 1 when 'M' THEN 2 WHEN 'R' THEN 3 END
) a

Answer 2

您希望优先处理地址。大多数数据库都支持窗口/分析功能，并提供了一种机制：

select p.first_name, a.address_1, a.zip, a.state
from person p join
     (select a.*,
             row_number() over (partition by a.person_id
                                order by (case when a.address_type = 'T' then 1
                                               when a.address_type = 'M' then 2
                                               when a.address_type = 'R' then 3
                                          end)
                               ) as seqnum
      from addresses a
     ) a
     on p.person_id = a.person_id and seqnum = 1;

编辑：

如果您想要特定类型的所有地址，只需将row_number()切换为dense_rank()：

select p.first_name, a.address_1, a.zip, a.state
from person p join
     (select a.*,
             dense_rank() over (partition by a.person_id
                                order by (case when a.address_type = 'T' then 1
                                               when a.address_type = 'M' then 2
                                               when a.address_type = 'R' then 3
                                          end)
                               ) as seqnum
      from addresses a
     ) a
     on p.person_id = a.person_id and seqnum = 1;

sql查询获取一个人的许多地址的一个地址

2 个答案: