Is there any needs of adding constraints for the DDL? - sql

Question

create table Country(
code char(3) PRIMARY KEY,
name varchar2(100) NOT NULL
);
create table Member(
firstname varchar(100) NOT NULL,
lastname varchar(100) NOT NULL,
title varchar(100) NOT NULL,
member_id INTEGER PRIMARY KEY,
Country_code char(3) NOT NULL REFERENCES Country(code)
ON DELETE CASCADE
ON UPDATE CASCADE
);
create table Athlete(
id integer NOT NULL REFERENCES Member(member_id)
ON DELETE NO ACTION
ON UPDATE CASCADE
);
create table Official(
id integer NOT NULL REFERENCES Member(member_id)
ON DELETE NO ACTION
ON UPDATE CASCADE
);
create table Staff(
id integer NOT NULL REFERENCES Member(member_id)
ON DELETE NO ACTION
ON UPDATE CASCADE
);
Create table Books(
when timestamp NOT NULL,
member_id integer NOT NULL REFERENCES Member(member_id),
start_time timestamp NOT NULL REFERENCES Journey(start_time),
start_date date NOT NULL REFERENCES Journey(start_date),
byStaff integer NOT NULL REFERENCES Staff(id)
);
create table Journey(
start_time timestamp PRIMARY KEY,
start_date date PRIMARY KEY,
member_id integer PRIMARY KEY REFERENCES Member(member_id),
nbooked integer NOT NULL,
departure varchar(100) NOT NULL REFERENCES Place(name),
arrival varchar(100) NOT NULL REFERENCES Place(name),
code varchar(100) NOT NULL REFERENCES Vehicle(code)
);
create table Vehicle(
code varchar(100) PRIMARY KEY,
capacity varchar(100) NOT NULL
);
create table Place(
name varchar(50) PRIMARY KEY,
address varchar(100) NOT NULL,
longitude float NOT NULL,
latitude float` NOT NULL
);
create table SportVenue(
name varchar(50) NOT NULL REFERENCES Place(name)
);
create table Accommodation(
name varchar(50) NOT NULL REFERENCES Place(name)
);
create table Event(
name varchar(100) PRIMARY KEY,
result_type varchar(100) NOT NULL,
time timestamp NOT NULL,
date date NOT NULL,
sport_name varchar(50) NOT NULL REFERENCES Sport(name),
);
For the DDL above, is there any needs of adding constraints for the DDL? If it needs to be modified, which constraints should be implemented? I am so confused on writing DDL... wef ewf ew fwe fewf wef oiwejf oiwej fioejwo ifjewo ifwjeoif jewoiew fiowefioje w
Thanks.

Answer 1

Constraints aka validation should be implemented from all sides of your application. Front-end, back-end, and your database. Otherwise, you would fail on the overall data integrity. So, the answer to your question is yes. Details depend on the nature of the data you will be working with.