✅ Interviewer: Count the number of employees in each department. 📊

Me: Using GROUP BY and COUNT():

SELECT d.dept_name,
       COUNT(e.id) AS employee_count
FROM employees e
INNER JOIN departments d
ON e.dept_id = d.dept_id
GROUP BY d.dept_name;

✔ Why it works: 
– COUNT() tallies employees per department by counting non-null IDs. 
– GROUP BY segments the results by department name for aggregated output. 
– INNER JOIN links employees to departments only where IDs match, avoiding nulls—add ORDER BY employee_count DESC to sort by largest teams first!

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