Relational Data model

What is a primary key in a relational database?

• a) A key used for indexing purposes

• b) A unique identifier for a row in a table

• c) A key used for foreign key constraints

• d) A key that allows null values

In a relational database, what does a foreign key represent?

• a) It represents a unique identifier for a row in a table.

• b) It establishes a relationship between two tables.

• c) It ensures that a column cannot contain NULL values.

• d) It is used for indexing purposes.

Which integrity constraint ensures that a column cannot have a NULL value?

• Entity Integrity

• Referential Integrity

• Domain constraints

• Joint constraints

___________________ is the mechanism the system provides to maintain primary keys. The primary key serves as a unique identifier for rows in the table.

• domain constraints

• referential integrity

• entity integrity

• key integrity

The value of an attribute in a table may be NULL because,

• a) the value is not known

• b) the value does not exist

• c) the value is not applicable

• d) all of the above

An attribute is a __________ in a relation.

• a) Row

• b) Column

• c)value

• d)relationship

What is the method of specifying a primary key in a database schema description?

• a) By writing it in bold letters

• b) By underlining it using a straight line

• c) By writing it in capital letters

• b) By underlining it using a dash line

Statement 1: A tuple is a row in a relation
Statement 2: Existence of multiple foreign keys in a same relation is possible

• a) Both the statements are true

• b) Statement 1 is correct but Statement 2 is false

• c) Statement 1 is false but Statement 2 is correct

• d) Both the statements are false

Constraints are the preferred method for enforcing data_______________

• a) security

• b) integrity

• c) inheritance

• d) validation

Which of the following can be addressed by enforcing a referential integrity constraint?

• a) StudentID must be unique

• b) When entering an order quantity, the user must input a number and not some text

• Information on the customer must be known before anything can be sold to that customer

• B. Certain fields are required such as customer_no and cannot input NULL value