Database Chapter 2

What is the purpose of a relational database management system (RDBMS)?

• To write complex algorithms

• To create and administer a relational database

• To analyze data patterns

• To design a database schema

Which of the following is a popular RDBMS package?

• MongoDB

• Redis

• Oracle RDBMS

• SQLite

What is the primary key in a relational database?

• A key that is shared between multiple tables

• A key used for encryption

• A key that uniquely identifies each record in a table

• A key used for sorting data

What does the Entity Integrity rule state?

• Every instance of an entity must have a unique primary key value

• The primary key must be unique and cannot be null

• Every foreign key value must match a primary key value

• The database must be consistent at all times

What is the purpose of the Restrict (select) operator in relational algebra?

• To find the difference between two relations

• To retrieve a horizontal subset of data from a relation

• To combine related tuples from several relations

• To select specified attributes from a relation

Which operator is used to combine the tuples of one relation with all the tuples of another relation?

• Join

• Restrict

• Project

• Cross product

What does the Union operator do in relational algebra?

• Finds the difference between two relations

• Selects specified attributes from a relation

• Combines all rows from two tables

• Finds the intersection of two relations

What is the purpose of the Intersect operator in relational algebra?

• Finds the intersection of two relations

• Finds the difference between two relations

• Combines all rows from two tables

• Selects specified attributes from a relation

What is the result of a Full Outer Join operation?

• Retains all rows from both tables

• Retains all rows from the left-hand table

• Retains all rows from the right-hand table

• Retains only the matched rows from both tables

What is the purpose of the Difference operator in relational algebra?

• Selects specified attributes from a relation

• Finds the difference between two relations

• Finds the intersection of two relations

• Combines all rows from two tables