Understanding Relational Concepts

What is the result of the UNION operation in Relational Algebra?

• A random selection of tuples from both relations without any specific criteria.

• A set of tuples that includes all tuples from both relations, with duplicates removed.

• A collection of tuples from one relation only.

• A set of tuples that includes all duplicates from both relations.

Explain the difference between SELECT and PROJECT in Relational Algebra.

• SELECT combines rows; PROJECT combines columns.

• SELECT filters rows; PROJECT selects columns.

• SELECT modifies data; PROJECT retrieves data.

• SELECT sorts data; PROJECT filters data.

What does the JOIN operation do in Relational Algebra?

• The JOIN operation separates tuples from two relations.

• The JOIN operation creates a new relation without any conditions.

• The JOIN operation deletes tuples from one relation.

• The JOIN operation combines tuples from two relations based on a specified condition.

How can you express a query to find all employees with a salary greater than 50000 in Relational Calculus?

• {e | Employee(e) AND e.salary > 50000}

• {e | Employee(e) OR e.salary > 50000}

• {e | Employee(e) AND e.salary < 50000}

• {e | Employee(e) AND e.salary = 50000}

What is the purpose of the WHERE clause in Relational Calculus?

• To sort records in ascending order.

• To filter records based on specified conditions.

• To define the structure of a database.

• To join multiple tables together.

Define the term 'tuple' in the context of Relational Algebra.

• A tuple is a collection of multiple relations.

• A tuple is a single row in a relation, consisting of a set of attribute values.

• A tuple is a type of database index.

• A tuple is a unique identifier for a database table.

What does Crows Feet notation represent in an Entity Relationship Diagram?

• Crows Feet notation indicates the color of entities.

• Crows Feet notation represents the cardinality of relationships between entities.

• Crows Feet notation is used to define the attributes of entities.

• Crows Feet notation represents the hierarchy of entities.

How do you indicate a one-to-many relationship using Crows Feet notation?

• A dashed line with arrows on both ends.

• A line with a crow's foot symbol at the 'many' end.

• A line with a single dot at one end.

• A solid line connecting both ends.

What is the primary key in an Entity Relationship Diagram?

• A description of the attributes of an entity.

• A visual representation of database relationships.

• A method for linking two tables together.

• A unique identifier for each entity in the database.

Explain the concept of an entity in an Entity Relationship Diagram.

• An entity is a graphical representation of a database schema.

• An entity is a real-world object or concept in an ERD that has attributes and can be related to other entities.

• An entity is a method used to query data from a database.

• An entity is a type of relationship between two objects.