How do you change a schema safely on a live system?
Model answer
Use versioned migrations in source control, make additive changes first (add a nullable column, backfill, then add constraints), deploy code that works with both old and new schema, and remove old columns later. Test on a copy of production data and know how to roll back.
Learn this topic
Keys and Table Design: Why Data Is Split Into Tables in the course SQL for Beginners: Learn Databases Step by Step.
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