How to Safely Backfill a BigQuery Table Without Breaking Your Data

Learn how to safely backfill historical data in a BigQuery table without replacing the entire table, breaking the schema, or creating duplicate records. In this practical example, I cover: • Using `DECLARE` to define a reusable date range • Previewing affected records before making changes • Using `DELETE` and `INSERT` to replace selected dates • Protecting the schema with explicit column names • Using transactions to keep the backfill safe • Validating the results and checking for duplicates • When you might use `MERGE` instead This pattern is useful when you need to correct or reload historical data while keeping records outside the backfill period unchanged. #BigQuery #GoogleCloud #SQL #DataEngineering #DataAnalytics