Database 101

What is a Database?

A database is a Self-Describing Collection of Integrated Records!

Characteristics of a Database

#1 - Self Describing

¨ A description of the data contained in the database – the Data Dictionary.

– From this external sources can learn what the DB contains from itself.

– You can change the DB w/out affecting other programs.

¨ This provides Program/Data Independence

#2 - Collection

¨ Files are a collection of

– Records are a collection of

• Fields are a collection of

– Characters are a collection of

• Bits

¨ This provides aggregation of Data

#3 - Integration

¨ DB contains Keys & Indexes and B-Tree

¨ Keys link the various Data Files

¨ B-Tree is balanced list of items

– All items are equal distance from the start

¨ This provides more efficient performance at the cost of more complex maintenance.

* So what’s the big deal?

¨ Data is not:

– Separate

– Isolated

– Duplicated

– Incompatible

But most importantly a DataBase is better able to represent the model the world that individuals work with!

What Components does the DB system include?

¨ Data

– Source Data

– Dictionary Data

– Integration Data

– Application Data

¨ Software:

– OS – Sun Solaris

– DBMS – IBM Unidata

– Language – Envision Basic

– Programs – Datatel & Custom

– Interface

¨ Hardware

– Server – Orion

– Clients – Desktop PC’s

– Printers

– Network Devices

Last.. But most importantly:

¨ Procedures – written documentation

¨ People

What does the DB do ?

¨ Stores data

¨ Retrieves data –

– Reports

– Screens

– Queries

– Exports

¨ Updates Data (adds, deletes, changes)

– Screens

– Forms

– Imports

– Processes/programs

¨ Enforce integrity rules

¨ Enforce security rules

¨ Provide coordination & control for multi-user processes.

¨ Provide backup and recover facilities.