You are given a table of daily marketing campaign activity exported from Resmed web analytics reporting. Write a SQL query to return total clicks by month for campaigns where the traffic source is Resmed.com and the campaign name is not null. Show the month in YYYY-MM format and sort the results by month ascending.
| Column | Type | Description |
|---|---|---|
| activity_idPK | INT | Unique row identifier |
| activity_date | DATE | Date of the campaign activity |
| campaign_name | VARCHAR(100) | Campaign name tracked in analytics |
| traffic_source | VARCHAR(50) | Source surface for the visit |
| clicks | INT | Number of clicks recorded that day |
| impressions | INT | Number of impressions recorded that day |