Glossary
Every term the courses use, defined in one line and then in a paragraph. Written to be read out of order.
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Answering a question that spans two tables.
Matching rows across tables using a key: orders with their customer names attached. Ordinary and fast when the columns involved are indexed, and very slow when they are not.
See also Foreign key, Index, Normalisation
A text format of keys and values.
How systems usually exchange structured data. Readable by every language and by you. It carries a shape both sides agreed on, but nothing enforces that agreement at runtime, which is why validation exists.
See also API, Contract, Validation
A signed token that carries its own data.
A token containing information, cryptographically signed so it cannot be altered. Needs no server lookup, which scales well, but cannot be revoked before it expires, so it must be short-lived.