Chapter 5 - Databases Flashcards
Database
Persistent (saved on secondary storage) organised store of data
Data integrity
Data reflecting reality
Validation
The process of checking data through software when it is input
Verification
Checking that the data entered is correct with duplicate file
Data matching
Compares different databases to look for particular relationships
Data mining
Looks in many different unrelated databases
Flat file database
Just rows (records) and columns (fields) - only 1 table
Data redundancy
Unnecessarily storing data in several places (repetition)
Relational databases
Stores data in separate tables which are linked on key fields
Entity
Something in real life about which data can be stored
DBMS
Database Management System is software that creates and manages a database and separates data from applications to minimise data redundancy
Transactions
A change in a database - must not damage data integrity
Record locking
Allows only one person to edit data at one time
Primary key
Unique identifier of a record which can be linked to a foreign key from another table
Forms
Provide a user friendly interface for data input or output
Reports
Physical outputs from a database
Queries
Used to extract data (using either a graphical interface or SQL (structured query language))
Modules
Units of software that take care of a particular function
What do databases need to be? (4)
1) Accurate
2) Up to date
3) Available
4) Protected
What do databases need to be protected against? (5)
1) Errors
2) Loss
3) Insufficient data
4) Inconsistencies
5) Unauthorised access
How can data be lost? (3)
1) Catastrophes e.g. flood
2) Accidental deletion
3) Malicious action
How can database problems be avoided? (4)
1) Validation
2) Frequent back ups
3) Locking action
4) Access levels
What do most people need to do to a database?
Create
Read
Update
Delete
What are the disadvantages of flat file databases? (2)
1) Very limited
2) Data redundancy - inconsistent updates
What does a DBMS do? (4)
1) Creates database applications
2) Protects data
3) Runs queries
4) Keeps data consistent and accurate
Why does data need to separated from applications? (4)
1) Programmers do not have to worry about damaging data
2) Applications can be written without restructuring data
3) Data easily shared between applications
4) Only one copy of data - no redundancy
What are the main features of a DBMS? (7)
1) Record locking
2) Creating tables
3) Graphs
4) Queries
5) Validation
6) Security
7) Automatic backups
Why are data types used?
Makes it easier for software to validate and process data, and decisions about space allocation can be made
What is a range check?
Checking if value entered fits into pre-determined range, data falls between two extreme values
What is a check digit?
Extra digit added to data produced by an algorithm
