ICT Notes 1/12/09

[unworthygoddess]

Yeah, I just needed this for school. And yes, I was at school when I did this.

... Oh, wow. I have another use for Lj. lol

Database and Information System

Database
- any collection of data stored in a way that enables people to add, find, sort, group, summarize and print data

- data
  - any unorganized text, graphics, sounds, or video
  - goes in

- information
  - data that has been processed so that it's organized in a way that people find meaningful and useful
  - goes out

Types of Database Programs

Database programs are application software used to create databases or work with the data in existing databases.

1. file management program - creates flat file databases, which only contain one file or table

2. database management systems - can manage multiple files or tables
     a. flat
     b. heirarchical
     c. network
     d. relational
            - data in several files is related through the use of a common ley field
            - a collection of two-dimensional tables

Advantage of Database Management Systems

1. Data Integrity - refers to the validility of the data contained in the database

2. Data Independence - data in the database is separate from the data that controls the applications

3. Avoidance of Data Redundancy

4. Data Security - means that the data stored in a database shouldn't be accessible to people who might misuse it

5. Data Maintenance - includes procedures for adding records, updating records, and deleting records for the purpose of keeping the database in optimal shape

Normalization of Database Tables

Normalization
  - process for assigning attributes to entities
  - reduces data redundancies and helps eliminate the data anomalies

Normalization works through a series of stages called forms:

1. First normal form (1NF)
2. Second normal form (2NF)
3. Third normal form (3NF)
4. Fourth normal form (4NF)

The highest level of database is not always desirable.

Conversation to First Normal Form
  - relational table must not contain repeating groups
  - repeating groups can be eliminated by adding the appropriate entry in at least the primary key column(s)

First Normal Form
  - describes the tabular format which:
     - all the key attributes are defined
     - there are no repeating groups in the table
     - all the attributes are dependent on the primary key