2022 cards

Question 1

DDL

Answer 1

defining the database schema

Question 2

SQL

Answer 2

Declarative/non - procedural DM.Requires a user to specify what data are needed without specifying how to get those data. Easy to learn and use.

Question 3

entity

Answer 3

an object that exists and is distinguishable from other objects.

Question 4

entity set

Answer 4

set of entities of the same type that share the same properties

Question 5

PK

Answer 5

A subset of the attributes form a primary key of the entity set; i.e., uniquely identifying each member of the set

Question 6

Do we represent entity or entity set in ER diagram?

Answer 6

Entity set

Question 7

Relationship

Answer 7

A relationship is an association among several entities

Question 8

Role in Relationship

Answer 8

Each occurrence of an entity set plays a “role” in the relationship. The labels “ course_id ” and “ prereq_id ” are called roles

Question 9

Types of Attributes

Answer 9

1. Simple and composite attributes
2. Single-valued and multivalued attributes
3. Derived attributes

Question 10

Attribute Domain

Answer 10

the set of permitted values for each attribute

Question 11

Composite attributes

Answer 11

Composite attributes allow us to divided attributes into subparts

Question 12

Mapping cardinalities of binary relationship

Answer 12

1. One to one
2. One to many
3. Many to one
4. Many to many

Question 13

Total participation

Answer 13

Total participation (indicated by double line): every entity in the entity set participates in at least one relationship in the relationship set.

Question 14

Partial Participation

Answer 14

Partial participation: some entities may not participate in any relationship in the relationship set.

Question 15

Weak entity set

Answer 15

A weak entity set is one whose existence is dependent on another entity, called its identifying entity. Instead of associating a primary key with a weak entity, we use the identifying entity, along with extra attributes called discriminator to uniquely identify a weak entity.

Question 16

Dependency between weak and identifying entity

Answer 16

Every weak entity must be associated with an identifying entity; that is, the weak entity set is said to be existence dependent on the identifying entity set. The relationship associating the weak entity set with the identifying entity set is called the identifying relationship.