Write a SQL query to find the top three most frequent security alerts per region over the last 30 days.
Use the provided regions and security_alerts tables. Include only named regions and non-null alert names recorded within the 30-day period.
region_name, alert_name, alert_count, and alert_rank.| Column | Type | Description |
|---|---|---|
| region_idPK | INT | Unique region identifier |
| region_name | VARCHAR(100) | Display name of the region |
| Column | Type | Description |
|---|---|---|
| alert_idPK | INT | Unique security alert identifier |
| region_id | INT | Region associated with the alert |
| alert_name | VARCHAR(100) | Security alert classification |
| occurred_at | DATE | Date when the alert occurred |