Question 1: GROUP BY Purpose and Function
What is the purpose of GROUP BY clause in SQL?
Question 2: HAVING vs WHERE Clause Usage
What is the difference between HAVING and WHERE clauses?
Question 3: GROUP BY with HAVING Clause
From an employees table (emp_id, name, department, salary), find departments with more than 5 employees and average salary greater than $60,000.
Question 4: SELECT Columns with GROUP BY Rule
What is the rule for SELECT columns when using GROUP BY?
Question 5: GROUP BY with Multiple Columns
How does GROUP BY work with multiple columns?
Question 6: HAVING without GROUP BY
Can HAVING clause be used without GROUP BY?
Question 7: GROUP BY with Complex HAVING Conditions
From a student_grades table (student_id, subject, grade, semester), find students who have taken more than 3 subjects and have an average grade between 85 and 95, showing student_id, subject count, and average grade.
Question 8: GROUP BY Multiple Columns with WHERE and HAVING
From a sales table (sale_id, product_id, category, region, sale_amount, sale_date), find total sales by category and region for sales in 2023, showing only combinations with total sales exceeding $10,000.
Question 9: GROUP BY with NULL Values
How does GROUP BY handle NULL values?
Question 10: Basic GROUP BY with Aggregate Functions
From an orders table (order_id, customer_id, order_date, total_amount), find the total sales amount and number of orders for each customer.