Quiz on SQL GROUP BY

What is the primary use of the GROUP BY clause in SQL?

Which function is most commonly used with GROUP BY?

What will the following query return?

SELECT department, COUNT(*) FROM employees GROUP BY department;

Which clause should come after `GROUP BY` in a SQL query?

What happens if a column in the SELECT clause is not in `GROUP BY` or inside an aggregate function?

Which query shows the highest salary in each department?

What does `GROUP BY 1` mean in this query?

SELECT city, COUNT(*) FROM customers GROUP BY 1;

Which of the following is TRUE about `HAVING` clause?

What is the output of this query?

SELECT COUNT(*), country FROM users GROUP BY country;

Can you use multiple columns in `GROUP BY`?

What happens if there is no `GROUP BY` but you use an aggregate function?

Which of these is invalid?

SELECT department, SUM(salary)
FROM employees
WHERE salary > 30000
GROUP BY department;

What’s the correct clause to filter grouped results?

SELECT department, AVG(salary)
FROM employees
GROUP BY department
??? AVG(salary) > 50000;

Which query shows the number of products sold per category?

What is the default sorting behavior of `GROUP BY` in SQL?