oracle 11g中如何使用SQL对象关系语句从两个表中提取数据

Question

我正在尝试使用对象关系方法解决以下查询，但不知道什么是正确的方法。

查找每个分行的储蓄账户数量，显示 号码和分行地址。

我创建了两个表并插入一些数据，如下所示：

--这是分支表：

create type Branch_Address as object(
street varchar2(20),
city varchar2(20),
p_code varchar2(10))
not final
/

create type Branch_Phone as object(
phone varchar2(20))
not final;
/

create type branch_type as object(
bID varchar2(10),
bAddress Branch_Address,
bPhone Branch_Phone)
/

create table branch of branch_type(
primary key (bID))
/

insert into branch values(
'901',Branch_Address('Nic Street','Jordan','ABH887A'),Branch_Phone('0335454888'));
/
insert into branch values(
'906',Branch_Address('East End Garden','California','L181QP'),Branch_Phone('07455668711'));
/
insert into branch values(
'912',Branch_Address('Fredrick Street','London','LA112AS'),Branch_Phone('02841124478'));
/

insert into branch values(
'924',Branch_Address('West Street','Cambridge','CA8L871'),Branch_Phone('04511477885'));

--这是账户表

create type account_type as object(
accNum int,
accType varchar2(15),
balance number, 
bID ref branch_type,
inRate number,
limitOfFreeOD number,
openDate DATE)
/
create table account_table of account_type(
primary key (accNum))
/

insert into account_table
select account_type('1001','current','820.50',ref(b),'0.005','800','01-May-11')
from branch b
where b.bID = '901';
/

insert into account_table 
select account_type('1010','saving','2155',ref(b),'0.02','0','08-Mar-10')
from branch b
where b.BID = '906';
/
insert into account_table 
select account_type('1002','current','2600',ref(b),'0.005','1000','10-Apr-13')
from branch b
where b.BID = '912';
/
insert into account_table 
select account_type('1112','saving','24000',ref(b),'0','1700','16-Jun-16')
from branch b
where b.BID = '924';
/

分支（bID、街道、城市、p_code、bPhone）

Account(accNum, accType, balance, bID, inRate, limitOfFreeOD, openDate)

粗体是主键 斜体是外键（在对象关系中，如果我是对的，我们不使用 Join）。

有什么帮助吗？谢谢。

Answer 1

您可以通过以下方式加入：

select b.bid, 
    (select count(1) from account_table a 
      where a.bid.bid = b.bid
      and a.acctype='saving'
      ) as num_accounts,
    b.baddress.street, b.baddress.city, b.baddress.p_code 
from branch b;

这更令人困惑，因为branch_type.bID 是varchar2(10) 而account_type.bID 是ref branch_type。我会将 account_type 上的 bID 重命名为 accBranch 之类的名称，以便更清楚地表明它不存储 ID，而是对整个对象的引用。

我没有测试过这个查询，但是你也可以把它写成一个连接（下）而不是一个子查询（上）。它们各有用途。

select b.bid, count(1) as num_accounts,
    b.baddress.street, b.baddress.city, b.baddress.p_code 
from branch b
join account_table a
  on a.bid.bid = b.bid
  and a.acctype='saving'
group by b.bid, b.baddress.street, b.baddress.city, b.baddress.p_code;