how to create inheritance table in oracle - sql

Question

there is table called event that act as parent the child inherit tables of event are special event and hotel event i have created the types as bellow but I'm contuse about how to create tables to these tables in oracle.I have referred most of the currently available solutions within Stack overflow, git hub etc. However, none of these solutions have worked out successfully.
Table types :
Event_t (
EventID:char(5),
EventType:varchar(20),
VenueName:varchar(50),
NoOfGuest:number(10)
) NOT FINAL
HotelEvent_t (
Date:date,
Price:numbr(8,2)
) UNDER Event_t
SpecialEvent_t (
BookingDate:date,
EndDate:date,
MenuNumber:number(2),
Reservation ref Reservation_t
) UNDER event_t
Thank you very much and any suggestion will be greatly appreciated.

Answer 1

Create your types using the correct syntax:
CREATE TYPE Event_t AS OBJECT(
EventID char(5),
EventType varchar(20),
VenueName varchar(50),
NoOfGuest number(10)
) NOT FINAL;
CREATE TYPE HotelEvent_t UNDER Event_t (
datetime date, -- Date is a keyword, try to use a different name.
Price number(8,2)
);
CREATE TYPE SpecialEvent_t UNDER event_t (
BookingDate date,
EndDate date,
MenuNumbers NUMBER(2),
Reservation ref Reservation_t
);
Then you can create an object table:
CREATE TABLE Events OF Event_T(
eventid CONSTRAINT Events__EventID__PK PRIMARY KEY
);
Then you can insert the different types into it:
INSERT INTO EVENTS VALUES(
HotelEvent_T(
'H1',
'HOTEL',
'Venue1',
42,
DATE '0001-02-03' + INTERVAL '04:05:06' HOUR TO SECOND,
123456.78
)
);
INSERT INTO EVENTS VALUES(
SpecialEvent_T(
'SE1',
'SPECIAL',
'Time Travel Convention',
-1,
SYSDATE,
TRUNC(SYSDATE),
0,
NULL
)
);
and get the data out of it:
SELECT e.*,
TREAT( VALUE(e) AS HotelEvent_T ).datetime AS datetime,
TREAT( VALUE(e) AS HotelEvent_T ).price AS price,
TREAT( VALUE(e) AS SpecialEvent_T ).bookingdate AS bookingdate,
TREAT( VALUE(e) AS SpecialEvent_T ).enddate AS enddate,
TREAT( VALUE(e) AS SpecialEvent_T ).menunumbers AS menunumbers
FROM Events e;
Which outputs:
EVENTID | EVENTTYPE | VENUENAME | NOOFGUEST | DATETIME | PRICE | BOOKINGDATE | ENDDATE | MENUNUMBERS
:------ | :-------- | :--------------------- | --------: | :------------------ | --------: | :------------------ | :------------------ | ----------:
H1 | HOTEL | Venue1 | 42 | 0001-02-03 04:05:06 | 123456.78 | null | null | null
SE1 | SPECIAL | Time Travel Convention | -1 | null | null | 2020-03-30 21:11:22 | 2020-03-30 00:00:00 | 0
db<>fiddle here

Answer 2

The typical way to create these tables in Oracle would be:
create table event_t (
event_id char(5) primary key not null,
event_type varchar2(20),
venue_mame varchar2(50),
no_of_guest number(10)
);
create table hotel_event_t (
event_date date,
price number(8,2),
event_id char(5),
constraint fk1 foreign key (event_id) references event_t (event_id)
);
create table special_event_t (
booking_date date,
end_date date,
menu_number number(2),
reservation_id char(5),
constraint fk2 foreign key (reservation_id)
references reservation_t (reservation_id),
event_id char(5),
constraint fk3 foreign key (event_id) references event_t (event_id)
);