design issues:

• minimize redundancy
• no inconsistency

Types of inconsistencies:

• update anomalies
• insertion anomalies
• deletion anomalies (lost information)

poorly designed example:

student records- name,course, phone #, major, professor, grade

name determins phone #,Major

update anomaly: change phone number in one course

decompose relation to fix.

decomposition

• name phone# major
• course professor
• name course grade

decomposition should be:

• content preserving
• relation preserving
• no free from interrelation join constraints (no consistency checks require join)

source psfile jl@crush.caltech.edu index