Chapter 10 : Managing A Database

• Database
• Collection of data organized in a manner that allows access,retrieval,and use of that data.
• Data
• Collection of unprocessed items
1. Text
2. Numbers
3. Images
4. Audio
5. Video
• Information
• Processed data
1. Documents
2. Audio
3. Images
4. Video
• Database software,often called a database management system (DBMS),allows users to:
1. Create a computerized database
2. Add,modify,and delete data
3. Sort and retrieve data
4. Create forms and reports from the data
• Data integrity identifies the quality of the data.
• Garbage in,garbage out (GIGO) points out the accuracy of a computer's output depends on the accuracy of the input.
• Valuable information should have the following characteristics:
1. Accurate
2. Verifiable
3. Timely
4. Organized
5. Accessible
6. Useful
7. Cost-effective

The Hierarchy of Data

• Character
• A character is only byte
• Numbers,letters,space,punctuation marks,or other symbols.
• Field
• A field is a combination of one or more related characters
1. Field name
2. Field size
3. Data type
• Common data types include:
1. Text
2. Numeric
3. AutoNumber
4. Currency
5. Date
6. Memo
7. Yes/No
8. Hyperlink
9. Object
10. Attachment
• Record
• A record is a group of related fields
• a primary key uniquely identifies each record.
• Data File
• A data file is a collection of related recrds.

Maintaining Data

• File maintenance refers to the procedure that keep data current
1. Adding records
2. Modifying records
3. Deleting records
• Users add new records to a file when they obtain new data.
• Users modify a record to correct inaccurate data or update old data.
• When a record no longer is needed,a user deletes it from a file.
• Validation compares data with a set of rules or values to find out if the data is correct
1. Alphabetic/Numeric check
2. Range check
3. Consistency check
4. Completeness check
5. Check digit
6. Other checks

File Processing Versus Databases

• File processing system
1. Each department has its own set of files
2. Used for many years
3. Have data redundancy
4. Isolate data
• Database approach
1. Programs and users share data
2. Reduce data redundancy 
3. Improve data integrity
4. Share data
5. Allows easier
6. Reduces development time
7. Can be more vulnerable

Database Management Systems

• A data dictionary contains data about each file in the database and each field in those files.
• A DBMS provides several tools that allow users and programs to retrieve and maintain data in the database
• 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.
• Form
•  a window on the screen that provides areas foe entering or modifying data in a database.
• Report generator
• allows users to design a report on the screen,retrieve data into the report design, and then display or print the report.

How to Use the Simple Query Wizard

1. Step 1: Select the fields from the Available Fields list you want to be displayed in the resulting query.
2. Step 2: Assign a name to the query,so that you can open it later.
3. Step 3: View the query results on the screen.

• A DBMS provides means to ensure that only authorized users access data at permitted times.
1. Access privileges
2. Principle of least privilege
• A DBMS provides a variety of techniques to restore the database to usable form in case it is damaged or destroyed
1. Backup
2. Log
3. Recovery utility
4. Continuous backup

Relational,Object-Oriented,and Multidimensional Databases

• A data model consists of rules and standard that define how the database organizes data.
• A relational database stores data in tables that consists of rows and columns.
1. Each row has a primary key.
2. Each columns has a unique name.
• A relationship is a link within the data.
•  Structured Query Language (SQL) is a query language that allows users to manage,update,and retrieve data.
• An object-oriented database (OODB) stores data in object.
• Examples of applications appropriate for an object-oriented database include:
1. Multimedia database
2. Groupware database
3. Computer-aided design database
4. Hypertext database
• A multidimensional database can store data in more than two dimensional of data.
1. sometimes known as a hypercube
2. 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 Databases

• Databases on the Web allow you to:
1. Shop for products or services
2. Buy or sell stocks
3. Search for a job
4. Make airline reservations
5. Register for college classes
6. Check semester grades

Database Administration

• It is important to have a carefully designed database.
• Database analysts and administrators are responsible for managing and coordinating all database activities.
• Database Analyst (DA)
1. Decides on proper field placement,defines data relationship,and identifies user's access privileges.
• Database Administrator (DBA)
1. Creates and maintains the data dictionary,manages security,monitors performance,and checks backup and recovery procedures
• Employees should learn how to use the data in the database effectively
1. Interact with database
2. Identify new data for the database
3. Maintain the database