REF querying with object-relational database - sql

Question

So currently my database stands as follows:
//branch table
create type branch_Type as object(bID number(6), branch_id ref branch_Type, b_street varchar2(20), b_city varchar2(20), b_p_code varchar2(8), b_bPhone number(14));
create table branch of branch_Type;
INSERT INTO branch VALUES(branch_Type('901', NULL, 'Market', 'Edinburgh', 'EH5 1AB', '01311235560'));
INSERT INTO branch VALUES(branch_Type('908', NULL, 'Bridge', 'Glasgow', 'G18 1QQ', '01413214556'));
insert into branch SELECT branch_Type('901', ref(e), b_street, b_city, b_p_code, b_bPhone) from branch e where e.BID = '901';
insert into branch SELECT branch_Type('908', ref(e), b_street, b_city, b_p_code, b_bPhone) from branch e where e.BID = '908';
//employee table
create type employee_Type as object(e_bid ref branch_Type, empID number(8), e_street varchar2(20), e_city varchar2(20), e_p_code varchar2(8), e_title varchar2(4), e_firstname_surname varchar2(20), emphomephone number(14), emp_mobile_1_2 number(22), supervisorID number(6), e_position varchar2(20), salary number(5), e_ninum varchar2(8), joindate date);
create table employee of employee_Type;
insert into employee select ref(e), '101', 'Dart', 'Edinburgh', 'EH1 05T', 'Mrs', 'Alison Smith', '01312125555', '0770562344307907812345', NULL, 'Head', '50000', 'NI001', '01-FEB-06'
from branch e where e.bid = '901';
insert into employee select ref(e), '105', 'New', 'Edinburgh', 'EH2 4AB', 'Mr', 'John William', 01312031990, 0790231455107701234567, '101', 'Manager', '40000', 'NI010', '04-MAR-07'
from branch e where e.bid = '901';
insert into employee select ref(e), '108', 'Old', 'Edinburgh', 'EH9 4BB', 'Mr', 'Mark Slack', 01312102211, NULL, '105', 'accountant', '30000', 'NI120', '01-Feb-09'
from branch e where e.bid = 901;
insert into employee select ref(e), '804', 'Adam', 'Edinburgh', 'EH1 6EA', 'Mr', 'Jack Smith', 01311112223, 0781209890, '801', 'Leader', '35000', 'NI810', '05-Feb-08'
from branch e where e.bid = 908;
select e_bid from EMPLOYEE where e_bid = '901'; //query I'm using
I am trying to query the employee table for the bid's that are referenced to branch table, but when I run the worksheet the script output tells me that I have no rows selected.

Answer 1

e_bid is a reference to the branch object and does not refer to the bID column contained in the object. You want:
SELECT e_bid
FROM EMPLOYEE
WHERE DEREF(e_bid).bID = 901;
I see no reason why your BRANCH_TYPE needs to contain a self reference (and when you set it you are creating a duplicate of the branch so there will be one instance where branch_id is NULL and another where it refers to itself).
You are repeating several structures across the tables and a better structure might be:
DROP SEQUENCE EMPLOYEES__ID__SEQ;
DROP TABLE EMPLOYEES;
--DROP TYPE EMPLOYEE_TYPE;
--DROP TABLE BRANCHES;
--DROP TYPE BRANCH_TYPE;
--DROP TYPE PHONENUMBER_TABLE_TYPE;
--DROP TYPE PHONENUMBER_TYPE;
--DROP TYPE ADDRESS_TYPE;
CREATE TYPE ADDRESS_TYPE AS OBJECT(
street varchar2(20),
city varchar2(20),
p_code varchar2(8)
);
/
CREATE TYPE PHONENUMBER_TYPE AS OBJECT(
international varchar2(4),
area varchar2(5),
local varchar2(8)
);
/
CREATE TYPE PHONENUMBER_TABLE_TYPE AS TABLE OF PHONENUMBER_TYPE;
/
CREATE TYPE BRANCH_TYPE AS OBJECT (
ID number(6),
Address ADDRESS_TYPE,
Phone PHONENUMBER_TYPE
);
/
create table branches of branch_type( ID PRIMARY KEY );
INSERT INTO BRANCHES VALUES (
901,
ADDRESS_TYPE( 'Market', 'Edinburgh', 'EH5 1AB' ),
PHONENUMBER_TYPE( '044', '1311', '235560' )
);
INSERT INTO BRANCHES VALUES (
908,
ADDRESS_TYPE( 'Bridge', 'Glasgow', 'G18 1QQ' ),
PHONENUMBER_TYPE( '044', '1413', '214556' )
);
create type employee_Type as object(
branch ref branch_type,
ID number(8),
address ADDRESS_TYPE,
title varchar2(4),
firstname_surname varchar2(20),
homephone PHONENUMBER_TYPE,
mobiles PHONENUMBER_TABLE_TYPE,
supervisor REF EMPLOYEE_TYPE, -- Change this to a REF
position varchar2(20),
salary number(5),
ninum varchar2(8),
joindate date
);
/
create table employees of employee_Type (
ID PRIMARY KEY
) NESTED TABLE mobiles STORE AS employees_mobiles;
CREATE SEQUENCE employees__id__seq;
insert into employees
select ref(b),
101, -- EMPLOYEES__ID__SEQ.NEXTVAL,
ADDRESS_TYPE( 'Dart', 'Edinburgh', 'EH1 05T' ),
'Mrs',
'Alison Smith',
PHONENUMBER_TYPE( '044', '1312', '125555' ),
PHONENUMBER_TABLE_TYPE(
PHONENUMBER_TYPE( '044', '7705', '623443' ),
PHONENUMBER_TYPE( '044', '7907', '812345' )
),
NULL,
'Head',
50000,
'NI001',
DATE '1906-02-01'
from branches b
where b.id = 901;
insert into employees
select ref(b),
102, -- EMPLOYEES__ID__SEQ.NEXTVAL,
ADDRESS_TYPE('New', 'Edinburgh', 'EH2 4AB'),
'Mr',
'John William',
PHONENUMBER_TYPE(NULL, '0131', '2031990'),
PHONENUMBER_TABLE_TYPE (PHONENUMBER_TYPE('44', '07902', '314551'), PHONENUMBER_TYPE('44', '07701', '234567')),
REF(s),
'Manager',
40000,
'NI010',
DATE '2007-03-04'
from branches b,
employees s
where b.id = 901
and s.id = 101;