// ============================================================================
// Query: Top N Resource Groups by Effective Cost (Last Month)
// Description:
//   Returns the top N resource groups by total effective cost for the last month.
//   Useful for identifying cost concentration and major spenders at the resource group level.
// Author: FinOps Toolkit
// Parameters:
//   N: Number of top resource groups to return (default: 5)
//   startDate: Start date for the reporting period (e.g., startofmonth(ago(30d)))
//   endDate: End date for the reporting period (e.g., startofmonth(now()))
// Output:
//   Each row represents a resource group with its total effective cost for the period.
// Usage:
//   Use this query to focus optimization and reporting on the highest-cost resource groups.
// Last Tested: 2025-05-17
// ============================================================================

// Top N Resource Groups by Effective Cost (Custom Date Range)
let N = 5;
let startDate = startofmonth(ago(30d)); // Default: last month
let endDate = startofmonth(now());
Costs()
| where ChargePeriodStart >= startDate and ChargePeriodStart < endDate
| summarize EffectiveCost = sum(EffectiveCost) by SubAccountName, x_ResourceGroupName
| top N by EffectiveCost desc