Chapter 10 : Managing a Database

Databases, Data, and Information

• Database - Collection of data organized 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 computerized database. Sort and retrieve 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 : 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. i) Field name ii) Field size iii) Data type.
• Common data types include : Text, Numeric, Date, Memo, Object, AutoNumber, Currency.
• A record is a group of related fields - A 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 ; i) Adding records ii) Modifying records iii) 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.
• Validation compares data with a set of rules or values to find out if the data is correct.

File Processing Versus Databases

• File processing system : i) used for many years. ii) have data redundancy. iii) isolate data
• Database approach : i) reduce data redundancy ii) share data iii) allows easier access.

Database Management Systems

• 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
• 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

• It is important to have a carefully designed database.
• Employees should learn how to use the data in the database effectively. Interact with database. Identify new data for the database. Maintain the database.