MYSQL - WHERE VS GROUP BY VS HAVING

Here is a clear, exam-ready tabular comparison of WHERE, GROUP BY, and HAVING with simple examples 👇

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Difference Between WHERE, GROUP BY, and HAVING

Feature	WHERE	GROUP BY	HAVING
Purpose	Filters rows	Groups rows with same values	Filters groups
Works on	Individual records	Aggregate data	Aggregate results
Used with aggregates	❌ No	✅ Yes	✅ Yes
Position in query	Before GROUP BY	After WHERE	After GROUP BY
Can use aggregate functions	❌ No (SUM, COUNT)	❌ No (only grouping)	✅ Yes
Example use	salary > 30000	GROUP BY department	HAVING COUNT(*) > 5

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Sample Table: employees

emp_id	name	department	salary
1	A	IT	50000
2	B	IT	60000
3	C	HR	30000
4	D	HR	40000
5	E	Sales	20000

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1️⃣ WHERE Example (Row-level filtering)

Question: Show employees with salary greater than 40,000.

SELECT * 
FROM employees
WHERE salary > 40000;

✔ Filters individual rows
✔ No aggregation

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2️⃣ GROUP BY Example (Grouping rows)

Question: Show total salary per department.

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

✔ Groups rows by department
✔ Uses aggregate function

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3️⃣ HAVING Example (Group-level filtering)

Question: Show departments where total salary is more than 80,000.

SELECT department, SUM(salary)
FROM employees
GROUP BY department
HAVING SUM(salary) > 80000;

✔ Filters after grouping
✔ Uses aggregate condition

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WHERE vs HAVING (Key Difference)

WHERE	HAVING
Filters rows	Filters groups
Cannot use aggregates	Can use aggregates
Executed before GROUP BY	Executed after GROUP BY

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Correct Order of Execution (Very Important for Exams)

FROM → WHERE → GROUP BY → HAVING → SELECT → ORDER BY

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💡 Easy Memory Trick

• WHERE = before grouping

• HAVING = after grouping

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