Computing Topic 5 Databases

A database is a persistent organised store of data on a computer system
The importance of databases
1. accurate
2. up to date
3. organised
4. protected from those who should not have access
5. available to those who need to use them
database administrators need to protect their data against:
1. errors
2. loss
3. unauthorised access
4. inconsistencies
5. insufficient data
errors in databases can result in:
1. financial loss
2. life or death situations such as incorrect navigational data for aircraft
Data security and integrity
1. security
  1. data can be lost because of:
    1. an accident
    2. flood or fire
    3. by an intruder
  2. can be protected by:
    1. making regular backups
    2. restricting data
    3. having a mirror database
    4. keep audit trails
2. integrity
  1. means the data reflects reality
  2. can be maximised by:
    1. suitable validation
    2. software preventing inconsistent states
Validation and verification
1. validation - process of checking data when it is input
2. verification - checking that the data inputted is correct
operations on databases can be listed under CRUD
1. create
2. read
3. update
4. delete
data matching and mining
1. matching compares different databases to look for relationships
2. mining looks in unrelated databases for relationships that were missed
data models
1. a model is a data structure that attempts to represent reality
2. flat file database - rows and columns
  1. rows are called records
  2. columns are called fields
3. data redundancy is repetition of data
4. hierarchical database
  1. useful making an inventory
5. relational database
  1. most useful
  2. most common
  3. separate, linked tables
  4. each table contains info on one entity
    1. info only stored once
DBMS
1. database management system
2. software that looks after databases
3. allows administrators to:
  1. create database applications
  2. protect data
  3. keep data consistent and accurate
transactions
1. when a change takes place in a database
multi-user databases
1. if two users try to modify data, one will fail
2. record locking - data can only be viewed until other users have finished modifying it
tools provided by DBMSs
1. tables
  1. structures where data is stored
2. linking tables
  1. avoids data redundancy
3. data types (text, number)
4. forms (UI)
5. reports
  1. summarise data
6. queries
7. module

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	Criado por Will Darby quase 9 anos atrás