1

我正在尝试创建一个整合多个单独选择查询的 SQL 视图。我在将各个 select 语句中的子句放入数据库视图时遇到了一些困难。

我的观点的简化版本是：

create or replace view TestView as
select 
 A.Name,
 B.Subscription,
 C.Expiry
from
 TestTableA as A left outer join TestTableB as B on A.ID = B.A_ID
 left outer join TestTableC as C on A.ID = C.A_ID;

我的观点有两个问题：

  • 在第一次加入时，我如何才能只选择 Subscription 是特定值的记录，如果不是该值，仍然检索 Name 和 Expiry 列（在这种情况下，Subscription 将为空）？

  • 在第二次加入时，我如何指定我只想要最近到期日期的记录？

以下是我的测试架构、示例数据和所需的结果集：

create table TestTableA
(
    ID int,
    Name varchar(32),
    Primary Key(ID)
);

create table TestTableB
(
    ID int,
    A_ID int,
    Subscription varchar(32),
    Primary Key(ID),
    Foreign Key(A_ID) references TestTableA(ID)
);

create table TestTableC
(
    ID int,
    A_ID int,
    Expiry date,
    Primary Key(ID),
    Foreign Key(A_ID) references TestTableA(ID)
);

create or replace view TestView as
select 
 A.Name,
 B.Subscription,
 C.Expiry
from
 TestTableA as A left outer join TestTableB as B on A.ID = B.A_ID
 left outer join TestTableC as C on A.ID = C.A_ID;

insert into TestTableA values (1, 'Joe');
insert into TestTableB values (1, 1, 'abcd');
insert into TestTableB values (2, 1, 'efgh');
insert into TestTableC values (1, 1, '2012-10-25');
insert into TestTableC values (2, 1, '2012-10-24');
insert into TestTableA values (2, 'Jane');

期望结果 1：

select * from TestView where Subscription is null or Subscription = 'efgh';

Joe, efgh, 2012-10-25
Jane, ,

预期结果 2：

select * from TestView where Subscription is null or Subscription = 'xxxx';

Joe, , 2012-10-25
Jane, ,
4

2 回答 2

2

我将使用简单的 SQL 编写查询
如果您有 SQL Server 2005 或更高版本，您可以outer apply使用min()

select 
    A.Name,
    B.Subscription,
    C.Expiry
from TestTableA as A
    left outer join TestTableB as B on A.ID = B.A_ID and B.Subscription in ('abcd', 'efgh') 
    left outer join
    (
        select min(T.Expiry) as Expiry, T.A_ID
        from TestTableC as T
        group by T.A_ID
    ) as C on A.ID = C.A_ID
于 2012-10-17T05:29:52.760 回答
0 
create or replace view TestView as
select 
  A.Name,
  B.Subscription,
  C.Expiry
from
  TestTableA as A left outer join TestTableB as B on A.ID = B.A_ID
  left outer join TestTableC as C on A.ID = C.A_ID;
where 
  B.Subscription is not null
  and C.Expiry between (now() - interval 1 minute) and now()
于 2012-10-17T05:31:01.360 回答