Design demand-side ads relational tables

You are designing the core relational data model for a demand-side advertising system. Create a normalized schema (tables + key columns + relationships) that supports: - **Advertiser** owns multiple **Campaigns**. - A campaign contains multiple **Ad Groups** (line items). - An ad group contains multiple **Ads/Creatives**. - Targeting settings (geo, device, audience), budgeting, start/end dates, pacing, and status (active/paused). - Reporting needs: join keys that make it easy to attribute an impression/click back to advertiser/campaign/ad group/ad. Explain: - Primary keys/foreign keys and cardinalities. - Which fields belong at campaign vs ad group vs ad. - How you would model targeting (as columns vs separate tables). - How you would handle versioning/audit (changes over time).