Informal Design Guidelines for Relational Schema
Informal Design Guidelines for Relational Schema Before introducing functional dependencies and normalization , relational database design uses informal guidelines to judge whether a schema is good or bad . These guidelines help detect design problems early , such as redundancy, anomalies, NULLs, and spurious tuples. There are four main informal design guidelines . Guideline 1: Impart Clear Semantics to Attributes Meaning A relation schema should have clear and unambiguous meaning . Each relation should represent only one entity type or one relationship type . Why this matters Users must easily understand what each tuple represents Queries become easier and less error-prone Prevents mixing unrelated real-world concepts Good Design Example EMPLOYEE(Ename, Ssn, Bdate, Address, Dnumber) Each tuple = one employee DEPARTMENT(Dname, Dnumber, Dmgr_ssn) Each tuple = one department These relations are easy to explain and interpret. Bad Design Exam...