Quiz for DISTINCT Keyword

Q1: What does the DISTINCT keyword do in a SELECT query?

A. Deletes duplicate rows B. Filters rows with NULLs C. Removes duplicates from result set D. Sorts results

Q2: What does the DISTINCT keyword do in SQL?

A. Removes duplicate rows B. Sorts the result C. Joins tables D. Limits rows returned

Q3: Which clause is typically used with DISTINCT?

A. FROM B. GROUP BY C. ORDER BY D. SELECT

Q4: Which of the following is correct syntax to retrieve unique department names?

A. SELECT ALL department FROM employees; B. SELECT DISTINCT department FROM employees; C. SELECT department DISTINCT FROM employees; D. SELECT UNIQUE department FROM employees;

Q5: Can DISTINCT be used with multiple columns?

A. Yes B. No C. Only with numeric columns D. Only with text columns

Q6: What is returned by: SELECT DISTINCT city, state FROM customers?

A. Only unique cities B. Only unique states C. All combinations of city and state D. Unique combinations of city and state

Q7: Which SQL statement returns unique job titles from employees table?

A. SELECT job_title FROM employees; B. SELECT ALL job_title FROM employees; C. SELECT DISTINCT job_title FROM employees; D. SELECT UNIQUE job_title FROM employees;

Q8: Does DISTINCT eliminate NULLs?

A. Yes B. No C. Only from numeric columns D. Only from text columns

Q9: What does SELECT DISTINCT salary FROM employees do?

A. Displays all salaries B. Displays unique salaries C. Displays max salary D. Displays duplicate salaries only

Q10: How many rows will SELECT DISTINCT department_id FROM employees return if there are 3 unique departments?

A. 3 B. 0 C. All rows D. Unknown

Q11: Which keyword is used to eliminate duplicates in SQL?

A. ORDER B. UNIQUE C. DISTINCT D. REDUCE

Q12: In SELECT DISTINCT name FROM users WHERE age > 25, what does DISTINCT apply to?

A. Only name B. Only age C. Entire result row D. None

Q13: What will SELECT DISTINCT COUNT(name) return?

A. Count of all names B. Count of distinct names C. Error D. Sum of names

Q14: Which query returns the number of unique countries from a table?

A. SELECT COUNT(country) FROM customers; B. SELECT DISTINCT COUNT(country) FROM customers; C. SELECT COUNT(DISTINCT country) FROM customers; D. SELECT UNIQUE country FROM customers;

Q15: Can DISTINCT be used with aggregate functions?

A. Yes B. No C. Only with COUNT() D. Only with SUM()

Q16: What will SELECT DISTINCT * FROM employees return?

A. All employees B. Only first employee C. All unique rows D. All columns only

Q17: Which one is valid to get distinct years from a date column?

A. SELECT DISTINCT date FROM orders; B. SELECT DISTINCT YEAR(order_date) FROM orders; C. SELECT UNIQUE order_date FROM orders; D. SELECT order_date DISTINCT FROM orders;

Q18: What will SELECT COUNT(DISTINCT employee_id) do?

A. Return total employees B. Return duplicate count C. Return count of unique employee_ids D. Return 0

Q19: What does SELECT DISTINCT 1+1 FROM dual return?

A. 2 B. 1 C. Error D. Distinct 1

Q20: Which returns total number of distinct salaries?

A. SELECT COUNT(salary) FROM employees; B. SELECT COUNT(ALL salary) FROM employees; C. SELECT COUNT(DISTINCT salary) FROM employees; D. SELECT salary FROM employees;

Q21: Which query returns distinct first and last name combinations?

A. SELECT DISTINCT first_name FROM employees; B. SELECT DISTINCT last_name FROM employees; C. SELECT first_name, last_name FROM employees; D. SELECT DISTINCT first_name, last_name FROM employees;