Problem Statement

From salaries_history, build monthly salary expense per department (month = first 7 chars of effective_date, YYYY-MM). Then compute month-over-month growth %, a 3-month rolling average, and a has_growth flag. Return department_name, expense_month, monthly_expense, prev_month_expense, mom_growth_pct, rolling_3month_avg, has_growth — ordered by department_name, expense_month.

Relevant Tables