ICT 301 Lecture Notes - Lecture 4: Decimal Mark, Unique Key, Requirements Analysis
21 Sep 2017
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Key: one attribute which contents are unique or multiple attributes which combined contents are unique. A terrible design consists of one table; First names and last names (many people can have the same first name, and many people can have the same last name) Students and classes (many students go to many classes, many classes have many students) Design by decomposition (part of normalization- logical design) Start from a big structure then logically break it down. M is the precision (number of total digits) D is the number of digits that can be stored following a decimal point. Useful when precision is not important (1. 00-0. 10= . 89) Ex: float (7,4) would look like 999. 99999. Floating would be good for math problems (more than 2 decimal points) whereas credit cards would be good for integers (2 decimal points) Timestamp is better than just using time because it"s only 1 bite more and gives you a lot more information.
