Joining Mismatched Datasets

Describe your approach to joining datasets with mismatched primary keys or differing aggregation levels.

Use the provided tables to reconcile daily campaign metrics with monthly campaign targets. Include only metric records whose external key maps to a campaign, while retaining target-only campaign months.

Output

1. One row per campaign and month
2. Columns: campaign_id, month_start, total_spend, total_conversions, target_conversions, and conversion_variance
3. Include all mapped metric months and target months, with missing measures represented as zero
4. Order by campaign_id, then month_start