CO SCI 136 Lecture Notes - Lecture 16: Query Optimization, Function Approximation, Data Modeling
Document Summary
Declarative: we tell the database what to do and not how to do a task. Transform a textual description into a set of concepts conveying exactly the same information. Inventor: prof p chen; 1976 [*: semantics-driven: our reasoning about the world, does not guarantee optimality in operations and query executions. Inventor: dr edgar codd; 1970: mathematics-driven: foundation of relational algebra, set theory, functional dependency theory, guarantees query optimization (heuristic optimization) Entities: concepts of interest (subjects: e. g. , lecturer, employee, vehicle, student, bank account. Attributes: properties of an entity (nouns: e. g. , name, id, number plate, balance, meta-data: domain (integer/real, characters, image, ), private or public or protected, unique, non-unique, encrypted, . Relationships: association between entities (verbs: e. g. , employee is working on a project, student attends a course, a lecturer teaches students, a supervisor (who is an employee) supervises another employee. Diagramming entities: drawn as a box with rounded corners labelled with the name of the concept that represents that entity.
