beginnerSQL Fundamentals — DDL, DML & Constraints
What are database constraints and why should you use them at the DB level rather than application level?
Constraints are rules enforced by the database engine: PRIMARY KEY, FOREIGN KEY, UNIQUE, NOT NULL, CHECK, DEFAULT. They should be at the DB level because: 1) Multiple applications may access the same database — app-level validation can be bypassed. 2) Database constraints are atomic within transactions — no partial violation. 3) Database constraints are documented in the schema — self-documenting.
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