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Topic
Schema migrations, referential integrity, constraints, cascade behavior, safe backfills, and data-retention effects.
Practice items tagged with SQL Migrations and Integrity.
Explains expand-and-contract migrations, backwards-compatible schema changes, backfills, rollout order, and rollback thinking.
Ranks duplicate import rows, previews the deletion set, and removes older copies with deterministic retention.
Uses a conditional update and transaction to prevent overselling while recording the reservation consistently.
Explains referential integrity, cascade delete trade-offs, restrict behavior, soft deletes, and operational safety.