sql查詢獲取一個人的多個地址的一個地址

Question

兩個表：人員和地址;連接條件是addresses.key_value = person.person_id。

有三個addresses.address_type：'R'，'M'，'T'。

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

如果address_type 'T' 然後取 'T' 否則，如果 'M' 其他 'R' 的地址。

對於每個地址，地址表中都有唯一的address_id。

Answer 1

您正在尋找地址的優先級。大多數數據庫支持窗口/分析功能，並提供一個機制：

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; 

編輯：

如果你想要一個給定類型的所有地址，只需切換row_number()到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; 

Answer 2

如果使用的是SQLSERVER 2005+，這可能是您的解決方案：

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