Consider an entity set Spaceship, with attributes name, sequence number (seq_num
ID: 3663973 • Letter: C
Question
Consider an entity set Spaceship, with attributes name, sequence number (seq_num), country, flight date, and captain. Assume that the following conditions hold: (1) No two space ships have the same name and sequence number (seq_num), (2) no two space ships have the same combination of captain and flight date, (3) each space ship has a name, a seq_num, and a country, and (4) not all space ships have been flown or have a captain.
(a) List all candidate keys and all superkeys for this entity set.
(b) Write a create table statement that defines a relation appropriate for this entity set.
Explanation / Answer
a.
Candidate Keys are: name and sequence number
Super Key : name, sequence number, country, flight date, caption
name, sequence number, country
name, sequence number, country, flight date
name, sequence number, flight date
name, sequence number, flight date, caption
name, sequence number, country, caption
b.
create table Spaceship(
name, varchar(50),
sqn_no varchar(10),
country varchar(10),
fight_date date,
caption varchar(20)
)