SQL 根据连接表的计数和/或标志选择标志

Question

我有一个客户表和一个地址表。

地址表有一个标志，它是 INVOICE、CORRESPONDENCE 或 DELIVERY。

一个客户可以有 0 到多个地址记录。

我希望能够查询这两个表并根据地址数据为每个客户生成一个标志 - 没有地址记录 = NONE，1 个或多个 INVOICE 记录 = HASINVOICE，没有 INVOICE 但有 1 个或多个其他 = HASOTHER

所以，对于以下数据：

+------------+---------+
| CustomerID |  Name   |
+------------+---------+
|          1 | Peter   |
|          2 | Ray     |
|          3 | Egon    |
|          4 | Winston |
|          5 | Dana    |
+------------+---------+

+-----------+------------+----------------+
| AddressID | CustomerID |  AddressType   |
+-----------+------------+----------------+
|         1 |          1 | INVOICE        |
|         2 |          1 | DELIVERY       |
|         3 |          2 | DELIVERY       |
|         4 |          2 | CORRESPONDENCE |
|         5 |          4 | INVOICE        |
|         6 |          5 | CORRESPONDENCE |
+-----------+------------+----------------+

我希望得到以下输出：

+------------+---------+-------------+
| CustomerID |  Name   | AddressFlag |
+------------+---------+-------------+
|          1 | Peter   | HASINVOICE  |
|          2 | Ray     | HASOTHER    |
|          3 | Egon    | NONE        |
|          4 | Winston | HASINVOICE  |
|          5 | Dana    | HASOTHER    |
+------------+---------+-------------+

对于 SQL 2000，这是否可能，使用单个查询而不使用游标？

Answer 1

我手边没有 2000 个实例（你真的应该升级，你落后了 4-5 个版本），但我认为这应该可行：

declare @Customers table (CustomerID int,Name varchar(10))
insert into @Customers (CustomerID,Name)
select 1,'Peter' union all    select 2,'Ray' union all
select 3,'Egon' union all    select 4,'Winston' union all
select 5,'Dana'

declare @Addresses table (AddressID int, CustomerID int,
                          AddressType varchar(30))
insert into @Addresses (AddressID,CustomerID,AddressType)
select 1,1,'INVOICE' union all    select 2,1,'DELIVERY' union all
select 3,2,'DELIVERY' union all    select 4,2,'CORRESPONDENCE' union all
select 5,4,'INVOICE' union all    select 6,5,'CORRESPONDENCE'

select
    c.CustomerID,
    c.Name,
    CASE MAX(CASE 
        WHEN a.AddressType = 'Invoice' THEN 2
        WHEN a.AddressType IS NOT NULL THEN 1
        END
    ) WHEN 2 THEN 'HASINVOICE'
    WHEN 1 THEN 'HASOTHER'
    ELSE 'NONE'
    END as AddressFlag
from
    @Customers c
        left join
    @Addresses a
        on
            c.CustomerID = a.CustomerID
group by
    c.CustomerID,
    c.Name

生产：

CustomerID  Name       AddressFlag
----------- ---------- -----------
5           Dana       HASOTHER
3           Egon       NONE
1           Peter      HASINVOICE
2           Ray        HASOTHER
4           Winston    HASINVOICE