Databases, Data, and Information
- Database - Collection of data organised in a manner that allows access, retrieval, and use of that data.
- Data - Collection of unprocessed items such as Text, Numbers, Images, Audio, Video
- Information - Processed data, Documents, Audio, Images, Video
- Database software, often called a database management system (DBMS), allows users to: Create a computerised database. Sort and retrieve data.
-Valuable information should have the following characteristics :
- Accurate
- Verifiable
- Timely
- Organized
- Useful
- Accessible
- Cost-effective.
The Hierarchy of Data
A character is one byte - Numbers, letters, space, punctuation marks, or other symbols.
A field is a combination of one or more related characters.
- Field name
- Field size
- Data type.
Common data types include :
- Text
- Numeric
- Date
- Memo
- Object
- AutoNumber
- Currency
A record is a group of related fields
-- primary key uniquely identifies each record
-A data file is a collection of related records.
Maintaining Data
File maintenance refers to the procedures that keep data current :
- Adding records
- Modifying records
- Deleting records.
Validation compares data with a set of rules or values to find out if the data is correct.
•Alphabetic/Numeric check
•Range check
•Consistency check
•Completeness check
•Check digit
•Other checks
File Processing Versus Databases
File processing system
File processing system
- used for many years
- have data redundancy
- isolate data
Database approach
•Programs and users share data
•Reduce data redundancy
•Improve data integrity
•Share data
•Allows easier access
•Reduces development time
•Can be more vulnerable
Database Management System
-A data dictionary contains data about each file in the database each field in those files.
-A DBMS provides tools allow users to retrieve and maintain data in the database
- Query language
- Query by example
- Form
- Report generator.
A query language consists of simple, English-like statements that allow users to specify the data to display, print, or store.
Query by example (QBE) provides a GUI to assist users with retrieving data.
A form is a window on the screen that provides areas for entering or modifying data in a database
A report generator allows users to design a report on the screen, retrieve data into the report design, and then display or print the report.
A DBMS provides a variety of techniques to restore the database to a usable form in case it is damaged or destroyed such as :
- Backup
- Log
- Recovery utility
- Continuous backup.
Relational, Object-Oriented, and Multidimensional Databases
A data model consists of rules and standards that define how the database organizes data.
A relational database stores data in tables that consists of rows and columns.
-Each row has a primary key
-Each column has a unique name.
A relationship is a link within the data.
An object-oriented database (OODB) stores data in objects.
Examples of applications appropriate for an object-oriented database include :
- multimedia database
- Groupware database
- Hypertext database.
A multidimensional database can store data in more than two dimensions of data
- Sometimes known as a hypercube
- Can consolidate data much faster than a relational database
A data warehouse is a huge database that stores and manages the data required to analyze historical and current transactions.
Web Database
Databases on the Web allow you to:
- Check semester grades
- Search for a job
- Buy or sell stocks
- Shop for products or services
- Make airline reservations
- Register for college classes.
Database Administration
Database analysts and administrators are responsible for managing and coordinating all database activities
Database Analyst (DA)
-Decides on proper field placement, defines data relationship, and identifies users’ access privileges
Database Administrator (DBA)
-Creates and maintains the data dictionary, manages security, monitors performance, and checks backup and recovery procedures
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