Branch Energy Spend vs Chain Average

Problem

Table: `energy_bill`

| Column Name | Type |
|---|---|
| bill_id | int |
| store_id | int |
| cost | int |
| billed_on | date |

`bill_id` is the primary key. Each row is one store's energy cost for a billing date.

Table: `store`

| Column Name | Type |
|---|---|
| store_id | int |
| region_id | int |

`store_id` is the primary key; `region_id` says which region the store belongs to.

For each calendar month, compare the average energy `cost` of each **region** against the average energy cost of the **whole chain** in that same month. Report `bill_month` (formatted `YYYY-MM`), `region_id`, and `verdict` which is `'higher'`, `'lower'`, or `'same'` depending on how the region average compares to the chain average. A bill counts toward both averages once. Order by `bill_month` descending, then `region_id` ascending.

Tables

Example rows — the live problem includes the full dataset.

Expected output

Your answer should return 4 rows with the columns bill_month, region_id, verdict.

Starter code (SQL)

SELECT *
FROM energy_bill;

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