Chapter 10: Databases and Information Management
Data and Information
How are data and information related?
· Computers process data into information
· Data is raw facts; information is data that is organized and meaningful
What is a database?
· Collection of data organized so you can access, retrieve, and use it
· Database software allows you to
o Create database
o Add, change, and delete data
o Sort and query database
· Database software also is called database management system (DBMS)
What is data integrity?
· Degree to which data is correct
· When database contains errors, it loses integrity
o Garbage in, garbage out
o (GIGO)
o Cannot create correct information from incorrect data
The Hierarchy of Data
What is a field?
· Combination of one or more characters
· Smallest unit of data user accesses
· Field name uniquely identifies each field
What are characteristics of a field?
· Data type
o Text – letters, numbers, special characters
o Numeric – numbers only
o Currency – dollar and cent amounts or numbers containing decimal values
o Date – month, day, year, and sometimes time
o Memo – lengthy text entries
o Yes/No – only the values Yes or No
o Hyperlink – Web address linking to a Web page
o Object – picture, audio, video or document created in other application
· Field size
What is a record?
· Group of related fields
· Must have key field
o Uniquely identifies each record in file
o Also called primary key
What is a data file?
· Collection of related records stored on disk
· Each record in file contains same fields
· Each field contains different data
· Database usually composed of group of related data files
Maintaining Data
What is file maintenance?
· Procedure that keeps data current
o Adding records
o Changing records
o Deleting records
What is validation?
· Validity check - analyzes entered data to help ensure it is correct
o Alphabetic Check
o Numeric Check
· Range Check – determines whether a number is within a specified limit
· Consistency Check – tests if the data in two or more associated fields is logical
· Completeness Check – certifies that all required data is present
What is a completeness check?
· Error message displays stating which required fields are blank
What is a check digit?
· Number(s) or character(s) appended to or inserted into primary key value
· Used to confirm accuracy of primary key value
File Processing Versus Databases
What is a file processing system?
· Each department or area within organization has own set of files
· Weaknesses
o Redundant data
o Isolated data
· Records in one file often do not relate to records in other files
o Problem: same customer may have different name or address in each file
What is the database approach?
· Many programs and users can share data in database
· Secures data so only authorized users can access certain data items
What are the strengths of the database approach?
· Reduced data redundancy
· Improved data integrity
· Shared data
· Reduced development time
· Easier reporting
What are the weaknesses of the database approach?
· Greater complexity
· Increased vulnerability
How do a database application and a file processing application differ in the way they might store data?
Database Management Systems
What is a database management system (DBMS)?
· Software that allows you to create, access, and manage a database
o Microsoft Access
o IBM’s DB2
o Oracle
What is a data dictionary?
· Contains data about each file in database and each field within those files
· Called “metadata”
What is a query language?
· Simple, English-like statements that allow you to retrieve data to display, print, or store
What is a query by example (QBE)?
· Program retrieves records that match criteria entered in form fields
What is a form?
· Window on screen that provides areas for entering or changing data in database
· E-form is similar, but used on Web
What is a report generator?
· Generates formatted report without user’s knowledge of programming
o Page numbers and dates
o Titles and column headings
o Subtotals and totals
· Comes with a database
What is data security?
· DBMS provides means to ensure only authorized users can access data with specified privileges
· Access privileges
· Define activities that specific user or group of users can perform
o Read-only privileges
§ User can retrieve data, but cannot change it
o Full-update privileges
§ User can retrieve and change the data
What is a log?
· Listing of activities that change database contents
· For every change, DBMS places three items in log file
o Before image
o Changed data
o After image
What is a recovery utility?
· Uses log file and/or backups to restore database when it is damaged or destroyed
o Rollforward
§ DBMS uses log to re-enter changes made to database since last save or backup
§ Also called forward recovery
o Rollback
§ DBMS uses log to undo any changes made to database during a certain period of time
§ Also called backward recovery
Relational, Object-Oriented and Multidimensional Databases
What is a data model?
· Every database and DBMS based on specific data model
· Composed of rules and standards
o Relational Databases
o Object-oriented and Object-relational Databases
o Multidimensional Databases
What is a relational database?
· Stores data in tables that consist of rows and columns
o Each row has primary key
o Each column has a unique name
What is normalization?
· Process designed to ensure data within relations (tables) contains least amount of duplication
What is relational algebra?
· Uses variables and operations to build new relations
· Used to manipulate and retrieve data
What is Structured Query Language (SQL)?
· Allows you to manage, update, and retrieve data
· Uses relational algebra
· Has special keywords and rules included in SQL statements
What is an object-oriented database (OODB)?
· Stores data in objects
o Object
§ Item that can contain both data and activities that read or process data
o Object query language (OQL)
§ Manipulates and retrieves object-oriented and object-relational data
· Advantages
o Can store more types of data
o Can access data faster
What are examples of applications appropriate for an object-oriented database?
· Multimedia databases
· Groupware databases
· Computer-aided design (CAD) databases
· Hypertext databases
· Hypermedia databases
What is a multidimensional database (MDDB)?
· Stores data in dimensions
· Advantage
o Can consolidate data much faster than relational database
What is a web database?
· Resides on a database server
· CGI (Common Gateway Interface) script
o Program
o Manages sending and receiving of data
o Between “front end” (usually a search engine)
o And database server
Database Administration
What is the role of the database analyst and administrator?
· Database analyst (DA)
o Focuses on meaning and usage of data
o Decides proper placement of fields, defines relationships among data, and identifies users’ access privileges
· Database administrator (DBA)
o Creates and maintains data dictionary, manages database security, monitors database performance, and checks backup and recovery procedures
What is the role of the employee as a user?
· Employee should learn how to utilize data in database
· Take part in designing database that will help achieve company’s overall goals
What are guidelines for developing a database?
· Determine the purpose
· Design the tables
· Design the fields
· Determine the relationships
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