SQL GROUP BY and Functional Dependencies: A Very Useful Feature | Java, SQL and jOOQ.

SQL GROUP BY and Functional Dependencies: A Very Useful Feature | Java, SQL and jOOQ.

Java, SQL and jOOQ. Best Practices and Lessons Learned from Writing Awesome Java and SQL Code. Get some hands-on insight on what's behind developing jOOQ. SQL GROUP BY and Functional Dependencies: A Very Useful Feature Relational databases define the term "Functional Dependency" as such (from Wikipedia): In relational database theory, a functional dependency is a constraint between two sets of attributes in a relation from a database. In other words, functional dependency is a constraint that describes the relationship between attributes in a relation. In SQL, functional dependencies appear whenever there is a unique constraint (e.g. a primary key constraint). Let's assume the following: CREATE TABLE actor ( actor_id BIGINT NOT NULL PRIMARY KEY, first_name VARCHAR(50) NOT NULL, last_name VARCHAR(50) NOT NULL ); It can be said that both FIRST_NAME and LAST_NAME ACTOR_ID column. Nice. So what? This isn't just some mathematical statement that can be applied to unique constraints.

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