Introduction to database systems 2

Question 1

What are relational keys?

Answer 1

One or more attributes that are needed to uniquely identify each tuple in a relation.

Question 2

What are the types of relational keys?

Answer 2

1. Primary key

2. Foreign key

Question 3

What is a super key?

Answer 3

Is an attribute that identifies ea tuple within a relation.

Question 4

What is a candidate key?

Answer 4

Is an attribute in a relation that can uniquely identify any tuple without referring to any other data

Question 5

What are alternate keys?

Answer 5

Candidate keys that are not selected to be the primary key.

Question 6

What are the properties of an attribute that qualifies to be a primary key?

Answer 6

ASK THE TEACHER !!!

Question 7

What is a foreign key?

Answer 7

An attribute, or set of attributes within one relation that matches a relational key of another relation.

Question 8

What is a composite key?

Answer 8

A relational key that is made up of more than one attribute.

Question 9

What is an integrity constraint?

Answer 9

An attribute that is associated with a domain such that the domain defines all acceptable data values that can be held by the attribute.

Question 10

What are the two types of integrity constraints?

Answer 10

1. Entity constraints
2. Referential constraints
3. General constraints

Question 11

What is entity constraint?

Answer 11

No attribute of a primary key can be null.

Question 12

What is referential constraint?

Answer 12

If a foreign key exists in a relation, the foreign key value must match a candidate key value of someplace in its home relation.

Question 13

What are general constraints?

Answer 13

Additional rules specific to your needs

Question 14

What are views?

Answer 14

This is the dynamic result of one or more relational operations operating on the base relations to define another relation without changing the original relation.
OR
The foreign key must have a relation with the candidate key in the base relation.