Relational Database Design Purpose & First Normal Form


  • Good Relational Design
    • Retrieve information easily, obtain all constraints, minimize redundancies, and have no ambiguous

Normally, The logical design is good enough because the ER diagram is carefully designed.

  • Large Schema

Suppose that instead of the schemas $course =(\underline{(c_name)},credits,domain,c_number)$ $offer=(\underline{p_code,c_name})$ we have a larger schema $course_info=(c_name,credits,domain,c_number,p_code)$ From the example, we see redundancy occurs.

  • Small Schema

Sometimes decompositions are useless. Sometimes naive decompositions create inconsistency.

Functional Dependency

For one attribute A of the schema, the other attributes it can be identified. A->B,C,D

First Normal Form 第一范式

A domain is atomic if its elements are considered to be indivisible units. A relational schema R is in first normal form if the domains of all attributes of R are atomic. Non-atomic values complicate storage and encourage redundant (repeated) storage of data. Atomicity is actually a property of how the elements of the domain are used.