How can we count employees in each department?
Combining LEFT JOIN with GROUP BY aggregates child records against parent dimensions accurately.
Department headcounts including 0-employee divisions, customer order counts.
SELECT d.department_name, COUNT(e.employee_id) AS employee_count
FROM departments d
LEFT JOIN employees e
ON d.department_id = e.department_id
GROUP BY d.department_name;Practice typing production-grade SQL code for JOIN with Aggregation.