Write a SQL query to join multiple fragmented datasets and resolve conflicting customer records based on incomplete demographic data.
Use the provided customer registry, fragmented profile records, and orders. Match profiles to registry customers using available demographic fields, retain only credible matches, select the strongest profile for each customer, and include unmatched registry customers.
Output
- One row per registry customer.
- Include canonical customer fields, the selected fragment ID and match score, matched fragment count, order count, total spend, and matched source names.
- Sort by
customer_id ascending. Return zero values for customers without orders.
