Overview and Introduction to Database Systems. There are 5 components of an information system. Data is the foundation of all information systems

Transcription

1 Database Systems Overview and Introduction to Database Systems Information Systems There are 5 components of an information system Hardware Software Data People Procedures Data is the foundation of all information systems Data is stored on hardware Data is organized by software Procedures are in place for handling data People access and use the data for many different purposes 1

2 What is Information? Data: Raw facts that have yet to be processed Information: Processed data; Data with meaning Data is processed and organized in a way that is meaningful to the user Can be summated data, ordered data, or just descriptive Knowledge: The result of what is learned from the information obtained After analyzing information, the user acquired knowledge that can be used to assist in the decision making process Wisdom: The result of experience over time through h the accumulation of information and knowledge. Data Processing Example A visit to the doctor Data: Stomach hurts, headache, fever Information: Symptoms can be organized to determine the problem Knowledge: After analyzing all the information, the doctor can determine the problem Wisdom: Experienced doctors can more easily diagnose problems based on years of experience. No need for consulting a manual 2

3 Information Effectiveness For information to be effective, you must have accurate and complete information in a timely manner. Choices are often made by the information and knowledge you have at the time In business, to be successful it is important that The right people have The right information at The right time! If I only knew then what I know now, I would have done things different! Bad Decisions If it s not broke, should we fix it? 3

4 Bad Decisions Information pertaining to the laws of physics would be helpful. Bad Decisions How was your job interview? More Bad Decision 4

5 Bad Decisions Facebook Newsfeed? Mobile Application? Timeline? Data Management Data must be properly formatted for storage, processing, and presentation Decision makers must have access to the information they need Data Management is a discipline that focuses on the proper generation, storage, and retrieval of data. Database Database Management Systems (DBMS) 5

6 What is a Database? A Database is a shared, integrated computer structure that stores end user data and metadata (data about data) Basically, the purpose of a database is to keep track of things Databases can store information that is much more complicated than spreadsheets or common lists of data Many types of databases Single User/Multi-User Desktop/Workgroup/Enterprise k /E Centralized/Decentralized Database Advantages Improved data sharing Better data integrity Minimized data inconsistency Improved data access Improved decision making Increased end-user productivity 6

7 History of Databases The roots of databases begin with file management systems History is preserved through database concepts (cavemen current) Concepts of databases span from ancient to modern times Examples can be seen in libraries, government, business, and medical records Dewey Decimal System Developed by Melvil Dewey in 1876 (10 classes, 10 divisions, 10 sections) 10 Main Classes 000 Computer science, information, and general works 100 Philosophy and psychology 200 Religion 300 Social Sciences 400 Languages 500 Science and Mathematics 600 Technology applied sciences 700 Arts and recreation 800 Literature 900 History, geography and biography 100 Divisions 330 Economics 1000 Sections.9 Geographical Treatment.04 European Economy European Economy 7

8 Reporting Creating reports using a file system can be difficult and time consuming Using the Dewey Decimal System Create a report listing all books written by each author Create a report listing all books related to Korean culture/history Create a report for all books published from Computerized databases increase the speed that these reports are generated Organizing i and dinformation i is important in order to generate accurate results in a timely manner Database design is critical!!! Organization and Design Data is the foundation of all decisions made within an organization Proper design and organization is important Maintaining data costs time and money The more data you have to manage, the more time and money it will cost Redundant data creates more data that needs to be manages Also creates risk of data mismanagement 8

9 Problems with Redundancy In a list (such as an excel spreadsheet) each row is intended to stand on its own. This results in information being entered multiple times Example Create a list of project Each project includes the project manager s name and phone number If a project manager has 10 projects, his information is listed 10 times In a list, each row may contain information on more than one subject As a result, information about one subject will only appear if information about a different subject exists Example List contains information about the project (ID, Project Name) List contains information about the project manager (Name, Phone Number) Data Redundancy Redundancy and multiple themes create modification problems Deletion problems Update problems Insertion problems Eliminating duplicate records results in More accurate data More manageable data More effective data More efficient data 9

10 Redundancy Example E.F. Codd , E.F. Codd proposed a relational model for databases Argued that report generation in file systems is difficult and time consuming Disconnects logical organization from physical storage methods Creates a logical schema for storing information so that it is easily accessible Improves efficiency and effectiveness The result is called: A Relational Database 10

11 Relational Database Designed to address many of the information complexity issues Stores information in tables Each topic is stored in its own table Breaks up a list containing many topics into several tables that are logically related to each other Creates relationship between tables A road map to data! Eliminates redundancy and saves time Time Consumption Relational Databases Development of relational databases takes a lot of time and money Users can access data much faster with more accurate results Lists and File Systems Development of a list is fairly easy and quick to create Creating reports from lists is very time consuming and expensive Redundant data causes problems with data accuracy Decision Using a list is easier on IT staff but creates more work for the users. Can potentially lead to poor decision making due to redundant (inaccurate) data Using a relational database requires a lot of time an effort from the IT staff but saves the users (decision makers) time and gives them more accurate data 11

12 Relationships Between Tables Redundancy Problem Solved 12

13 Maintaining the Database Terminology Data: Raw Facts Field (Attribute): Used to define and store data Record (Tuple): A logically connected set of one or more fields that describe a person, place, or thing File (Table): A collection of related records that define an entity Entity: The subject of the table 13

14 The Database A self-describing collection of related records Self-describing means The database itself contains the definition of its structure Metadata is data describing the structure of the database data Tables within the relational database are related to each other Database Management System Database Management Systems (DBMS) is a collection of programs that manage the database structure and controls access to the data stored in the database. Servers as an intermediary between database applications and the database. Manages and controls database activities Creates, processes, and administers the database and its controls 14

15 Data Dictionary Stores the definition of data elements and their structure for the DBMS Metadata repository Describes the database (or databases) and its structure Used for maintaining the DBMS Used for documenting the DBMS Naming Fields Table names and field names should be descriptive Easy to read and understand First letter always begins with a lower case Example: name If two words are combined, the first letter of second word is capitalized Example: firstname Abbreviations are used whenever possible Example: fname Avoid using keywords that are often use in programming languages Example: save (the save table for saving information) 15

16 Functions of a DBMS Create databases Create tables Create supporting structures Read database data Modify database data (insert, update, delete) Maintain database structures Enforce rules Control concurrency Provide security Perform backup and recovery Microsoft Access Microsoft Access is an example of a DBMS It can be used to: Create a database Modify a database Insert, update, or delete data in the database Generate reports Define the data dictionary Etc. Let s take a look at Microsoft Access 16

17 DBMS Security Who should use the DBMS? Should users have access to the DBMS? Why or why not? Database Applications A database application is a set of one or more computer programs that serves as an intermediary between the user and the DBMS Functions of database applications include: Create and process forms Process user queries Create and process reports Execute application logic Control database applications 17

18 Personal Databases Personal database systems typically: Have one application Have only a few tables Are simple in design Involve only one computer Support one user at a time What uses would a personal database have? (Discuss) Enterprise Database Systems Enterprise database systems typically: Support several users simultaneously Include more than one application Involve multiple computers Are complex in design Have many tables Have many databases Examples include Oracle SQL Server DB2 Etc. 18

19 Enterprise Database Systems Centralized versus Decentralized Centralized Database Information is stored in one central location Typically stored at the corporate office Developed by small group Decentralized Database Information is stored in multiple locations Database is broken up by functional area Each functional area maintains their database Requires complex design for decentralized relational databases Developed by multiple teams 19

20 Backup and Security Backing up your data and protecting it is very important There are many threats to the security of your data People accessing the system Physical security of the hardware Natural disasters In the event that a threat should occur, you must be able to recover Full backup Incremental backup Transactional backup Off-site backups Structured Query Language Structured Query Language (SQL) is an international standard for creating, processing and querying databases and their tables SQL is sometimes pronounces as Sequel Many database applications use SQL to retrieve, format, report, insert, delete, and/or modify data for users Uses standard English to execute commands Example: SELECT columnname FROM tablename WHERE condition=true Executing commands COMMIT; Used to save results from a query ROLLBACK; Used to undo the results of a query 20

21 SQL Example SQL Example SELECT CUSTOMER.CustomerLastName, FROM CUSTOMER.CustomerFirstName, CustomerFirstName CUSTOMER.Phone, COURSE.CourseDate, ENROLLMENT.AmountPaid, COURSE.Course, COURSE.Fee CUSTOMER, ENROLLMENT, COURSE WHERE CUSTOMER.CustomerNumber = ENROLLMENT.CustomerNumber AND COURSE.CourseNumber = ENROLLMENT.CourseNumber; 21

22 SQL Example Results Conclusion 5 components of an information systems DB is the foundation of all information systems Data Information Knowledge Data management is important Relational Databases & Database Management Systems Eliminate data redundancy Structure Query Language 22