Context

You’re on-call for a fintech platform that processes ~20M card transactions/day and stores data in a PostgreSQL data warehouse used for fraud monitoring, chargeback investigations, and regulatory audits. A nightly ETL job loads data into a staging table (stg_authorizations) and then merges it into a curated fact table. Last week, an engineer tried to “clear the staging table” and accidentally broke downstream dashboards for the fraud team. The incident review found confusion between TRUNCATE, DELETE, and DROP, especially around rollback behavior, identity sequences, and dependencies.

Core Question

Explain the difference between TRUNCATE, DELETE, and DROP in SQL. In your answer, address the following:

1. What each statement does to table data and table metadata (schema).
2. Transaction and rollback behavior: under what conditions can each be rolled back? (Call out that behavior varies by database engine.)
3. Performance and logging differences (row-by-row vs bulk deallocation, WAL/redo logging implications).
4. Constraints and dependencies: how foreign keys, triggers, and views behave (e.g., TRUNCATE ... CASCADE, trigger firing differences).
5. Identity/auto-increment behavior: what happens to sequences/identity counters.
6. Provide a practical recommendation for a staging-table ETL pattern: when to use TRUNCATE, when to use DELETE with a WHERE clause, and when DROP is appropriate.

Scope Guidance (What a strong answer includes)

• Use concrete examples tied to production operations (staging tables, audit requirements, and incident prevention).
• Mention at least one database-specific nuance (e.g., PostgreSQL vs MySQL vs SQL Server) and how you’d verify behavior.
• Discuss safety practices: permissions, dry-runs, using transactions, and avoiding accidental destructive operations.