如何有条件地从多个地址中选择一个地址

Question

我有这样的桌子：

CustomerID | Address  | Address Type
100000001  | addressA | Mailing Address
100000001  | addressB | Registered Address
100000001  | Null.    | Office Address

一个客户可能有多个地址。在这种情况下，我只想选择一个地址：

1. 如果Office Address不为null，那么我将从Office Address获取Address。如果“办公室地址”为空，则转到数字2。

2. 检查注册地址是否不为空，然后从注册地址中获取地址。

Answer 1

在有条件的情况下将TOP 1与ORDER BY一起使用

select top 1 *
from   address
where  CustomerID = @CustomerID
and    Address is not null
order by case when AddressType = 'Office' then 1
              when AddressType = 'Registered' then 2
              else 3
              end

Answer 2

CREATE TABLE CUSTOMER (CUSTOMERID INT , ADDRESS VARCHAR(500) , ADDRESSTYPE VARCHAR(25));

INSERT INTO CUSTOMER VALUES (100000001,'ADDRESSA' ,'MAILING ADDRESS');
INSERT INTO CUSTOMER VALUES (100000001,'ADDRESSB',  'REGISTERED ADDRESS');
INSERT INTO CUSTOMER VALUES (100000001, NULL ,'OFFICE ADDRESS');

SELECT 
    ISNULL(
        (SELECT ADDRESS FROM CUSTOMER WHERE CUSTOMERID = 100000001 AND ADDRESSTYPE = 'OFFICE ADDRESS' ) ,
        (SELECT ADDRESS FROM CUSTOMER WHERE CUSTOMERID = 100000001 AND ADDRESSTYPE = 'REGISTERED ADDRESS' )
    ) 

Answer 3

select * from customer 

select  max(customerID) customerID ,max(Address) Address ,max(Addresstype) Addresstype
from customer  
where address is not null
group by customerID

输出