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


we have a larger schema


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.

Table Of Contents
Relational-Database-Design-Purpose-&-First-Normal-Form
Functional Dependency
First Normal Form 第一范式