Quiz for GROUP BY

Q1: What does the GROUP BY clause do in SQL?

A. Sorts the records B. Groups records with identical values C. Deletes duplicate rows D. Updates grouped data

Q2: Which of the following is a valid use of GROUP BY?

A. To group rows based on conditions B. To group columns with constraints C. To group rows with the same value in specified column(s) D. To sort data in descending order

Q3: Which clause is often used with GROUP BY?

A. ORDER BY B. WHERE C. HAVING D. SET

Q4: Which aggregate function is commonly used with GROUP BY?

A. ROUND() B. DATE() C. COUNT() D. LENGTH()

Q5: Can you use GROUP BY with multiple columns?

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

Q6: What happens if you omit a non-aggregated column from the GROUP BY clause?

A. SQL groups automatically B. An error is thrown C. It returns all rows D. The first row is selected

Q7: Which clause determines the grouping behavior in SQL?

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

Q8: Which aggregate function returns the maximum value in a group?

A. AVG() B. MAX() C. SUM() D. MIN()

Q9: What does the following SQL return? SELECT department, COUNT(*) FROM employees GROUP BY department;

A. Employee list B. Total salary C. Number of employees in each department D. Error

Q10: What is the purpose of the HAVING clause in conjunction with GROUP BY?

A. To group aggregated rows B. To filter grouped data C. To limit rows D. To delete duplicates

Q11: Which SQL keyword is used to filter rows before grouping?

A. HAVING B. GROUP BY C. ORDER BY D. WHERE

Q12: What will SELECT city, COUNT(*) FROM customers GROUP BY city; return?

A. Cities only B. Customers only C. Number of customers per city D. Error

Q13: Which of these is invalid in a GROUP BY clause?

A. GROUP BY 1 B. GROUP BY column_name C. GROUP BY alias_name D. GROUP BY *

Q14: What will SELECT product_id, SUM(quantity) FROM sales GROUP BY product_id; return?

A. All product details B. Total quantity per product C. Product prices D. Quantity per category

Q15: Is ORDER BY mandatory when using GROUP BY?

A. Yes B. No C. Only with MAX() D. Only in subqueries

Q16: What happens if a column in SELECT is not part of GROUP BY or an aggregate function?

A. SQL executes normally B. Warning shown C. Error is raised D. NULL is returned

Q17: Which clause is evaluated first in a SQL query with GROUP BY?

A. HAVING B. SELECT C. WHERE D. GROUP BY

Q18: Can you use GROUP BY with JOINs?

A. No B. Only with INNER JOIN C. Yes D. Only with UNION

Q19: How does GROUP BY affect NULL values?

A. Ignores NULL B. Groups all NULLs together C. Throws error D. Skips NULL rows

Q20: Which keyword is used to filter grouped rows in SQL?

A. HAVING B. WHERE C. FILTER D. JOIN