DataBolt

All Lessons

Introduction to SQL

SQL Lesson 1: Your Sample Database

SQL Lesson 2: SELECT — Reading data

SQL Lesson 3: WHERE — Filtering rows

SQL Lesson 4: AND, OR, NOT

SQL Lesson 5: BETWEEN, IN, LIKE

SQL Lesson 6: NULL — The Mystery Value

SQL Lesson 7: ORDER BY

SQL Lesson 8: LIMIT & OFFSET

SQL Lesson 9: Aggregate Functions

SQL Lesson 10: GROUP BY

SQL Lesson 11: HAVING

SQL Lesson 12: INNER JOINs

SQL Lesson 13: LEFT JOINs

SQL Lesson 14: RIGHT JOINs

SQL Lesson 15: SELF JOINs

SQL Lesson 16: UNION JOINs

SQL Lesson 17: Joining Multiple Tables

SQL Lesson 18: Subqueries

SQL Lesson 19: CTEs (WITH)

SQL Lesson 20: CASE Statements

SQL Lesson 21: Window Functions

SQL Lesson 22: String Functions

SQL Lesson 23: Date & Time Functions

SQL Lesson 24: INSERT, UPDATE, DELETE

SQL Lesson 25: CREATE TABLE & DDL

SQL Lesson 26: Indexes & Performance

SQL Lesson 27: Transactions & ACID

SQL Lesson 28: SQL Execution Order

SQL Lesson 29: 50 Practice Problems

CHAPTER 12

HAVING

Filtering groups — the WHERE clause for aggregates.

IN THIS CHAPTER

Why WHERE cannot be used with aggregate functions
HAVING to filter grouped results
The definitive WHERE vs HAVING comparison

12.1 - HAVING Basic

Departments with more than 2 employees

SELECT department, COUNT(*) AS headcount
FROM employees
GROUP BY department
HAVING COUNT(*) > 2;

12.2 - WHERE vs HAVING - The Golden Rule

	WHERE	HAVING
Filter	Individual rows	Groups (after GROUP BY)
Runs	Before GROUP BY	After GROUP BY
Aggregates?	No - COUNT/AVG not allowed here	Yes - purpose-built for them
Example	WHERE salary > 60000	HAVING AVG(salary) > 60000

❌ Common Mistake: Writing WHERE COUNT(*) > 2 throws an error. WHERE runs before aggregation — the COUNT values do not exist yet at that point in execution. Use HAVING.

✅ Interview Tip 'What is the difference between WHERE and HAVING?' is asked in almost every data-related SQL interview. Answer: WHERE filters rows before grouping; HAVING filters groups after aggregation.

Exercise 👇

Exercise:

Tasks

1.👉Find departments that have more than 2 employees.

2.Find departments where total salary is greater than 150000.

3.Find departments where average salary is greater than 60000.

4.Find departments where the highest salary is greater than 80000.

Stuck? Read this task's