Glossary · Phase 7 · Software engineering
Composite key
A primary key made of two or more columns together, like (member_id, trip_id).
Try it now
Ask of each column: is it a fact about the member, about the trip, or about this person on this trip?
Learn it properly
Designing a database · From one big table to related tables: keys, constraints, many-to-many and a loader that is safe to rerun. About 40 minutes.
Other terms from the same lesson
- database normalization: Splitting data into related tables so each fact is stored exactly once.
- link table: A table whose rows each connect one row of one table to one row of another, plus facts about that connection.
- logical key: The real-world identifier for a row, such as an email or SKU, kept unique even when tables link by an id.
- many-to-many: A relationship where each side can link to many of the other, like members and trips, stored with a link table.
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