Computing Topic 5 Databases

Computing Topic 5 Databases

1. A database is a persistent organised store of data on a computer system

2. The importance of databases

   • accurate
   • up to date
   • organised
   • protected from those who should not have access
   • available to those who need to use them

3. database administrators need to protect their data against:

   • errors
   • loss
   • unauthorised access
   • inconsistencies
   • insufficient data

4. errors in databases can result in:

   • financial loss
   • life or death situations such as incorrect navigational data for aircraft

5. Data security and integrity

   • security
     • data can be lost because of:
       • an accident
       • flood or fire
       • by an intruder
     • can be protected by:
       • making regular backups
       • restricting data
       • having a mirror database
       • keep audit trails
   • integrity
     • means the data reflects reality
     • can be maximised by:
       • suitable validation
       • software preventing inconsistent states

6. Validation and verification

   • validation - process of checking data when it is input
   • verification - checking that the data inputted is correct

7. operations on databases can be listed under CRUD

   • create
   • read
   • update
   • delete

8. data matching and mining

   • matching compares different databases to look for relationships
   • mining looks in unrelated databases for relationships that were missed

9. data models

   • a model is a data structure that attempts to represent reality
   • flat file database - rows and columns
     • rows are called records
     • columns are called fields
   • data redundancy is repetition of data
   • hierarchical database
     • useful making an inventory
   • relational database
     • most useful
     • most common
     • separate, linked tables
     • each table contains info on one entity
       • info only stored once

10. DBMS

    • database management system
    • software that looks after databases
    • allows administrators to:
      • create database applications
      • protect data
      • keep data consistent and accurate

11. transactions

    • when a change takes place in a database

12. multi-user databases

    • if two users try to modify data, one will fail
    • record locking - data can only be viewed until other users have finished modifying it

13. tools provided by DBMSs

    • tables
      • structures where data is stored
    • linking tables
      • avoids data redundancy
    • data types (text, number)
    • forms (UI)
    • reports
      • summarise data
    • queries
    • module