DBMS Theory QUIZ-II

You have a relation called "Employees" that contains information about employees, including their salaries. You want to find the average salary of all employees. Which relational algebra operation would you use?

• SELECT

• PROJECT

• AGGREGATE

• JOIN

With SQL, how can you return the number of not null records in the “Persons” table?

• SELECT COUNT() FROM Persons

• SELECT COLUMNS() FROM Persons

• SELECT COLUMNS(*) FROM Persons

• SELECT COUNT(*) FROM Persons

You have a "Products" relation that contains information about products, including their prices. You want to find the products with a price greater than $100. What relational algebra operation would you use?

• SELECT

• PROJECT

• JOIN

• DIFFERENCE

SQL query to find the temperature in increasing order of all cities.

• SELECT city FROM weather ORDER BY temperature

• SELECT city, temperature FROM weather

• SELECT city, temperature FROM weather ORDER BY temperature

• SELECT city, temperature FROM weather ORDER BY city

In a database, you have a "Sales" relation that contains information about sales transactions, including the salesperson's name. You want to find the distinct names of salespeople who made sales. What relational algebra operation would you use?

• SELECT

• PROJECT

• UNION

• DISTINCT

You have a "Students" relation that contains information about students, including their ages. You want to find the average age of all students. Which relational algebra operation would you use?

• SELECT

• PROJECT

• AGGREGATE

• JOIN

You have two relations, "Employees" and "Departments." The "Employees" relation contains employee information, and the "Departments" relation contains department information. You want to find all employees in the "HR" department. What relational algebra operation would you use?

• SELECT

• PROJECT

• JOIN

• INTERSECT

SQL query to find all the cities whose humidity is 95.

• SELECT city WHERE humidity = 95

• SELECT city FROM weather WHERE humidity = 95

• SELECT humidity = 89 FROM weather

• SELECT city FROM weather

Which of the following statement is true?

• DELETE does not free the space containing the table and TRUNCATE free the space containing the table

• Both DELETE and TRUNCATE free the space containing the table

• Both DELETE and TRUNCATE does not free the space containing the table

• DELETE free the space containing the table and TRUNCATE does not free the space containing the table

Find all the cities with temperature, condition and humidity whose humidity is in the range of 63 to 79.

• SELECT * FROM weather WHERE humidity IN (63 to 79)

• SELECT * FROM weather WHERE humidity NOT IN (63 AND 79)

• SELECT * FROM weather WHERE humidity BETWEEN 63 AND 79

• SELECT * FROM weather WHERE humidity NOT BETWEEN 63 AND 79