DBMS Quiz 4CSE1 2025 LAB-4

What is an entity in an Entity-Relationship model?

• An entity is a random collection of data without any specific attributes.

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

• An entity is a process that describes how data is manipulated.

• An entity is a distinct object or thing in the real world that can be identified and has attributes.

Define the term 'relationship' in the context of ER diagrams.

• A relationship in ER diagrams is a type of entity.

• A relationship in ER diagrams represents the association between entities.

• A relationship in ER diagrams is a graphical representation of data storage.

• A relationship in ER diagrams defines the attributes of an entity.

What is the purpose of normalization in database design?

• To increase data duplication for faster access.

• To simplify complex queries by merging tables.

• The purpose of normalization is to reduce data redundancy and improve data integrity.

• To enhance the visual representation of data in reports.

Explain the difference between primary key and foreign key.

• A primary key is always a string, while a foreign key is always an integer.

• A primary key is used for indexing, while a foreign key is used for sorting records.

• A primary key can be duplicated across tables, while a foreign key cannot.

• A primary key uniquely identifies a record in a table, while a foreign key links to a primary key in another table.

What is the role of a composite key in a database?

• A composite key is used to encrypt data in a database.

• The role of a composite key in a database is to uniquely identify a record using multiple columns.

• A composite key is a single column that can be used to identify records.

• A composite key is a type of index that speeds up database queries.

List and explain any two types of data integrity constraints.

• Check Constraint

• Primary Key Constraint, Foreign Key Constraint

• Unique Key Constraint

• Not Null Constraint

How does relational algebra differ from SQL?

• Relational algebra is a theoretical framework; SQL is a practical implementation with a specific syntax.

• Relational algebra is used for data visualization; SQL is used for data storage.

• Relational algebra requires a database connection; SQL does not.

• Relational algebra is a programming language; SQL is a query language.

What is a weak entity and how is it represented in an ER diagram?

• A weak entity is a type of relationship that does not require a strong entity for identification.

• A weak entity is an entity that depends on a strong entity for its identification, represented by a double rectangle in an ER diagram.

• A weak entity is represented by a dashed line in an ER diagram.

• A weak entity is an independent entity represented by a single rectangle in an ER diagram.

Write a SQL query to find the total number of employees in a table named 'Employees'.

• SELECT COUNT(employee_id) FROM Employees;

• SELECT COUNT(*) FROM Employees;

• SELECT TOTAL(employees) FROM Employees;

• SELECT SUM(*) FROM Employees;

Consider a database table named Employees with columns EmployeeID, Salary, and Department. You need to give a 10% raise to all employees in the 'Marketing' department, but only to those earning less than $60,000. Which of the following UPDATE statements is the most appropriate and safest to achieve this?

• UPDATE Employees SET Salary = Salary * 1.1 WHERE Department = 'Marketing';

• UPDATE Employees SET Salary = Salary + (Salary * 0.1) WHERE Department = 'Marketing' AND Salary < 60000;

• UPDATE Employees SET Salary = Salary * 1.1 WHERE Department = 'Marketing' AND Salary < 60000;

• UPDATE Employees SET Salary = Salary * 1.1; WHERE Salary < 60000 AND Department = 'Marketing';