create table user_accounts
(
ID number,
fname varchar2(50),
lname varchar2(50),
username varchar2(20),
password varchar2(20)
);;

create table credit_cards
(
ID number,
cc_number varchar(20),
exp_date date
);;
alter table user_accounts add constraint pk_id primary key(ID);;
alter table user_accounts add constraint unique_username unique(username);;
alter table credit_cards add constraint fk_id foreign key(ID) references user_accounts(ID);;
insert into user_accounts values(1,'John','Smith','jsmith','j123$');;
insert into credit_cards values(1,'3243242342','07-JUN-04');
select * from user_accounts;
insert into user_accounts values(2,'John','Smith','jsmith1','j123$');;
insert into credit_cards values(2,'3243242342','07-JUN-04');
select * from credit_cards;
alter table credit_cards drop constraint fk_id;
alter table user_accounts drop constraint pk_id;
alter table user_accounts add constraint pk_id primary key(ID) ;;
alter table credit_cards add constraint fk_id foreign key(ID) references user_accounts(ID) on delete CASCADE;;
delete from user_accounts where id=1;
alter table credit_cards add constraint fk_id foreign key(ID) references user_accounts(ID) on delete cascade;
update user_accounts set fname='Joe' where ID=1;
create table backup as select * from user_accounts;
select * from backup;
insert into user_accounts values(3,'John','Smith','jsmith2','j123$');;
create view users_view as select * from user_accounts;
select * from users_view;
insert into user_accounts values(4,'John','Smith','jsmith4','j123$');;
update users_view set lname='New' where id=4;
select fname,lname,cc_number from user_accounts, credit_cards where user_accounts.ID=credit_cards.ID;
select user_accounts.ID,fname,lname,cc_number from user_accounts, credit_cards where user_accounts.ID=credit_cards.ID;
create view myview as select user_accounts.ID,fname,lname,cc_number from user_accounts, credit_cards where user_accounts.ID=credit_cards.ID;
select * from myview;