Prof. Cantonjos Components of Database System DATA HARDWARE SOFTWARE USER Advantages ECONOMY OF SCALE - The concentration of applications in one location allows for the possibility of smaller numbers of larger and more powerful computers, which usually results in an economy of scale. The same economy of scale may be realized by the concentration of technical expertise. In general, economy of scale refers to the fact that the collective cost of several combined operations may be less than the sum of the cost of the individual operations. GETTING MORE INFORMATION FROM SAME AMOUNT OF DATA – The primary goal of a computer system is to form data (recorded facts) into information gain by processing these facts. SHARING OF DATA – The data can be stored among authorized users, allowing users access to more of the data. BALANCING CONFLICTING REQUIREMENT – For the database approach to function adequately, there must be a person or a group within the organization in charge of the database itself. This group is often Database Administration (DBA). ENFORCEMENT OF STANDARDS – With the central control mentioned in the previous paragraph, DBA can ensure that standards for such things as data names, usages & formals are followed uniformly throughout the organization. CONTROLLED REDUNDANCY – In the database approach since there is only one occurrence of each faculty member, this redundancy is eliminated. INTEGRITY – An integrity constraints in a rule that data in the databases must follow. A database satisfies all integrity constraints that have been established. Note: Integrity – accuracy of encode SECURITY – Security is the prevention of access to the database by unauthorized users. Incription – transformation of program into different meaning FLEXIBILITY AND RESPONSIVENESS – The flexibility furnished by the DBMS to locate and access data in a number of different ways aids programmers in developing new programs to satisfy user requests. INCREASED PROGRAMMER PRODUCTIVITY – studies have shown that on the coverage they will be two to four times more productive (i.e. a new application can be developed in one quarter to one half of the time it would take if it were straight file oriented approach. ) IMPROVED PROGRAM MAINTENANCE – Many changes to the structure of the data itself may not require maintenance to existing application programs. DATA INDEPENDENCE – Without such independence, changes to the database structure to improve performance are to meet changing corporate requirements become very complex. Data independence occurs when the structure of the database can change without requiring the programs that access the database to change. Disadvantages of Database Size Complexity Cost Additional hardware requirements Higher impact of a failure Recovery more difficult USERS Users of the database A. ACTORS ON THE SCENE – People whose jobs involves the day to day use of large databases 1. DATABASE ADMINISTRATORS - The chief administrators to oversee and manage the resources DATABASE Designers – responsible for identifying data to be stored in the database and for choosing appropriate structures to represent and store this data. END USERS – Persons whose jobs require access to the database for querying, updating and generating reports CASUAL END USERS NAÏVE END USERS SOPHISTICATED END USERS SYSTEM ANALYST AND APPLICATION PROGRAMMERS – Determine the requirements of end users, especially naïve and parametric end-users and develop specifications for canned transactions that meet this requirements. Workers behind the scene DBMS DESIGNERS AND IMPLEMENTORS TOOL DEVELOPERS OPERATORS AND MAINTENANCE PERSONNEL nd 2 Lecture RELATIONAL DATABASE MANAGEMENT SYSTEMS Designed to create, maintain, manipulate, modify and delete information in a relational database. Structured Database Model Hierarchical Model - Publisher Authors Manuscript Bookstore Deliveries Payment Things you can do with RDBMS CREATE A DATABASE – Personal and business database need to be created and RDBMS programs will help facilitate this process. Database creation is made easier and faster because of these programs. INFORMATION STORAGE – Once your database is created, it is now easy to add information into your database. For example, if you have a list of mp3 music in your computer, as new music becomes available you simply add this data into your database and categorize it to the attributes you have created, whether it is a jazz or rock, classical or modern, you can also rate it as one of the favorites. A database program allows you to add, organize, modify, edit and delete your information as you deemed fit. INFORMATION RETRIEVAL – Since your database is created in a structured fashion, it is easy to retrieve data. In databases, the means to retrieve data is by query. Query is a request for specific information from the created database. For example, when you were young your parents used to play music from the “Eagles” band entitled “Hotel California”. If they want to play that song, they can retrieve it from the database and play the music. INFORMATION MANAGEMENT – RDBMS programs allow you to utilize and modify the information in a database according to your needs. You may add attributes for example to your music database so that you would be able to sort and arrange it according to artist, date the music was released and so on. INFORMATION ANALYSIS – The most important function of a database is using it. Data accumulated and gathered is an asset in this Information Age. For example in business, you would be able to track the interest of a certain generation of people in their interest of clothing, music, shoes and eating habits. PRINT AND SHARE INFORMATION – For purposes of a “hard copy” information may be printed and stored as back up copy in case the digital copy of the database gets corrupted or damaged. Printed information is also necessary for people who are not used to viewing data in the computer monitor and prefers them on paper. The internet revolution has also made it possible to place your data on a website, send via email and shared to others over a network. Qualities of Good Database Information ACCURATE INFORMATION ORGANIZED TIMELY INFORMATION VERIFIABLE INFORMATION ACCESSIBLE INFORMATION ECONOMICAL INFORMATION (Cost Effective) USEFUL INFORMATION ASSIGNMENT #2 MODELS OF DBMS with graphical illustration Submit it in a sliding folder rd 3 Lecture STRUCTURED DATABASE MODELS - HIERARCHICAL MODEL - NETWORK MODEL - RELATIONAL MODEL - ENTITY-RELATIONSHIP MODEL - DIMENSIONAL MODEL - OBJECT – RELATIONAL MODEL DATABASE TERMINOLOGIES DATA – IT IS A NUMBER OR VALUE FOUND AND STORED IN THE DATABASE. DATA IS STATIC BECAUSE IT REMAINS THE SAME UNTIL IT IS MODIFIED BY A PROCESS INFORMATION – IT IS A DATA THAT HAS BEEN PROCESSED THEREBY MAKING IT RELEVANT AND MEANINGFUL TO THE PERSON VIEWING IT. NULL – IT IS USED TO REPRESENT A VALUE THAT IS UNKNOWN OR MISSING. A NULL VALUE IS NEITHER A ZERO NOR BLANK. TABLE - IT IS THE MAIN STRUCTURE IN THE RELATIONAL DATABASE. IT IS COMPOSED OF ATTRIBUTES (FIELDS) AND DOMAIN (RECORDS) FILE ORGANIZED COLLECTION OF DATA ABOUT AN ENTITY. EXAMPLE: FOR A BOOKSTORE, A FILE CALLED “ BRANCH” CAN CONTAIN ALL THE DATA ABOUT A PARTICULAR BOOKSTORE BRANCH.” RECORD IT REFERS TO A SPECIFIC PERSON, PLACE, THING OR EVENT. RECORD IS ALSO KNOWN AS THE “TUPLE” IN THE RELATIONAL DATABASE TERMINOLOGY. IT PERTAINS TO STRUCTURE IN THE DATABASE TABLE REPRESENTING A UNIQUE INSTANCE OF A SUBJECT. FIELD IT IS THE SMALLEST STRUCTURE OF A DATA FROM A LARGER DATABASE STRUCTURE IN A RELATIONAL DATABASE. A FIELD CAN STORE DATA IN A DATABASE AND REPRESENT A CHARACTER OF THE SUBJECT TO WHICH DATABASE TABLE IT RESIDES. VIEW IT IS ALSO KNOWN AS A VIRTUAL TABLE. IT IS CALLED A VIRTUAL TABLE SINCE IT DOES NOT HOLD DATA ON ITS OWN; RATHER IT GETS DATA FROM THE TABLE TO WHICH IT IS BASED. AND SINCE IT COMES FROM OTHER TABLES IT IS COMPOSED OF SEVERAL FIELDS COMING FROM ONE OR MORE DATA. KEYS THESE ARE FIELDS THAT SERVE SPECIFIC PURPOSES WITHIN A TABLE. THERE ARE 2 TYPES OF KEYS, THE PRIMARY KEY AND THE FOREIGN KEY. THE PRIMARY KEY IS A FIELD THAT UNIQUELY IDENTIFIES A RECORD IN THE TABLE. THE FOREIGN KEY IS A SPECIAL FIELD THAT ESTABLISHES A RELATIONSHIP BETWEEN 2 TABLES. RELATIONSHIPS THEY EXIST WHEN 2 OR MORE TABLES HAVE CONNECTION OR ASSOCIATION. RELATIONSHIPS RELATIONSHIPS IN RELATIONAL DATABASE EXIST WHEN 2 OR MORE TABLES ARE CONNECTED BY THE FOLLOWING CONDITIONS: 1. PRIMARY KEY 2. FOREIGN KEY LINKING TABLE IS A TABLE THAT ESTABLISHES A CONNECTION BETWEEN 2 OR MORE TABLES. TYPES OF RELATIONSHIPS ONE-TO-ONE RELATIONSHIPS THIS RELATIONSHIP EXISTS BETWEEN TABLES WHEN ONLY ONE RECORD OF THE FIRST TABLE IS RELATED TO ONLY ONE RECORD OF THE SECOND TABLE. EXAMPLE: EMPLOYEES TABLE EMPLOYEE ID FIRST NAME LAST NAME 001 MICHAEL CRUZ 002 MATTHEW FRANCISCO EMPLOYEE ID DAILY RATE INCENTIVE PERCENTAGE 001 350.00 5% 002 250.00 10% SALARY TABLE ONE TO MANY RELATIONSHIPS THIS RELATIONSHIP EXISTS BETWEEN TABLES WHEN ONE RECORD OF THE FIRST TABLE CAN BE RELATED TO ONE OR MORE RECORDS TO A SECOND TABLE, BUT ONLY ONE RECORD FROM THE SECOND TABLE CAN BE RELATED TO A SINGLE RECORD IN THE FIRST TABLE. THIS RELATIONSHIP IS THE MOST COMMON RELATIONSHIP THAT EXISTS BETWEEN TABLES AND HELPS TO REDUCE OR ELIMINATE DUPLICATE DATA. EXAMPLE: A Publisher is associated with all the books that it publishes while a book is associated with a publisher. PUBLISHER CODE NAME COUNTRY 198801 JEMMA INC. PHILS. ISBN PUBLISHER CODE BOOK TITLE 9781235 198801 CREATIVE DESIGN 9781236 198801 SPREADSHEETS 9781237 198801 OFFICE PROD. MANY-TO-MANY RELATIONSHIPS THIS RELATIONSHIP EXISTS BETWEEN TABLES WHEN ONE RECORD OF THE FIRST TABLE CAN BE RELATED TO ONE OR MORE RECORDS TO A SECOND TABLE AND ONE RECORD FROM THE SECOND TABLE CAN BE RELATED TO ONE OR MORE RECORDS TO THE FIRST TABLE. THE CONNECTION BETWEEN THE TWO TABLES WILL BE DIFFICULT TO ESTABLISH AND WILLRESULT TO REDUNDANT DATA IN ONE OF THE TABLES. STUDENTS TABLE STUDENT NUMBER FIRST NAME LAST NAME 20091 AGNES ONG 20043 RICHARD TAN SUBJECTS TABLE CODE NAME FACULTY ID MATH01 MATH 8852 SCIENCE 01 SCIENCE 8821 DESIGNING A DATABASE DEFINE THE PURPOSE OF YOUR DATABASE DETERMINE THE TABLES THAT YOU NEED IN THE DATABASE DETERMINE THE FIELDS THAT YOU NEED IN THE DATABASE IDENTIFY UNIQUE FIELD VALUES THAT WILL ALLOW ACCESS TO CONNECT INFORMATION STORED IN A SEPARATE TABLE DETERMINE THE RELATIONSHIPS BETWEEN TABLES TEST THE DESIGN BY ENTERING THE SAMPLE DATA CHARACTERISTICS OF A WELL DESIGNED DATABASE MODIFYING DATA IS EASY. CHANGES TO THE VALUE OF ONE FIELD WITHIN THE TABLE SHOULD NOT AFFECT THE VALUES OF THE FIELDS IN THE TABLE. RETRIEVING INFORMATION IS EASY. EXTRACTING DESIRED INFORMATION FROM TABLES WITH WELL DEFINED RELATIONSHIPS SHOULD MAKE ACCESSING AND RETRIEVING DATA A LOT FASTER. DEVELOPING AND BUILDING USER APPLICATION IS EASY. DATA MANIPULATION WOULD BE THE MAIN FOCUS OF PROGRAMMING AND NOT SOLVING THE PROBLEMS ASSOCIATED WITH A POORLY DESIGNED DATABASE MAINTAINING THE STRUCTURE IS EASY. CHANGES MADE TO ANY TABLE OR COLUMNS SHOULD NOT AFFECT OTHER TABLES OR COLUMNS. ADDING AND DELETING DATA IS EASY.