Database Management Systems 1


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An introduction to data and the need for database management systems

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Database Management Systems 1

  1. 1. Database Management Systems An Introduction to Databases and the Relational Database Model By Nickkisha Farrell, BSc IT, Dip Ed January 2014
  2. 2. IN THIS PRESENTATION What is data anyway? The traditional/file oriented approach The database approach Advantages of databases 2 Database Management Systems - An overview
  3. 3. WHAT IS DATA ANYWAY? • Raw Fact or value • In order to derive meaningful information from data some operation must be performed on it. • For Example: • Weight= 112 is data • Name = ‘Shanice’ is another piece of data 3
  4. 4. THIS THING CALLED DATA • Why is Data important? Data is important because every decision that happens in the world is based on some data • It is one of the most precious resources for businesses and individuals alike. • For example, if Jim wants to buy a tablet, he will use the data available to make the best decision regarding the model. Data such as its cost, market value, etc. 4
  5. 5. DATABASES • Data is ubiquitous - it is every-where! All aspects of the modern business feed off huge amounts of data. • Data quantities are increasing at exponential rates. • Databases provide a flexible, reliable and secure way to organize this data. 5
  6. 6. DATABASES • A Database is a group of related files • For example: • A Database on students may contain the names, addresses and courses of students in a college. • Are databases the only option? Couldn’t we just use files, folders, paper and pencils to store data? 6
  7. 7. THE PROBLEM WITH TRADITIONAL FILE STORAGE • Data quantities are increasing at alarming rates, this poses a challenge to storage by traditional techniques • Data redundancy: • Presence of duplicate/recurrence of data in multiple files, leads to wasting of storage space • Data inconsistency: • Same attribute has different values or different application maybe be used hence 1 piece of data may be formatted several different ways thus interoperability of data between programs prove difficult (Windows versus Mac) 7
  8. 8. THE PROBLEM WITH TRADITIONAL FILE STORAGE • Program-data dependence: • When changes in program requires changes to data accessed by program. • Lack of Integrity - Data is susceptible to human error (eg American versus British style of recording dates) • Concurrent Access anomalies When many people try to write a piece of data concurrently • Poor security • Lack of data sharing and availability 8
  9. 9. THE DATABASE MANAGEMENT SYSTEM APPROACH • A Database Management System[DBMS] is a combination of related files (the database) and programs which allow users to work on data (the management system) • DBMS eliminates the various problems that are associated with file storage by: • Interfacing between applications and physical data files • Separates logical and physical views of data 9
  10. 10. THE DATABASE MANAGEMENT SYSTEM APPROACH • The DBMS: • Controls redundancy • Eliminates inconsistency • Uncouples programs and data • Enables organization to centrally manage data and data security • In real-life, DBMS are widely used in almost every industry. - For example in banking - to manage customer accounts - In travel - to manage reservations for airline companies 10
  11. 11. DATABASE CONCEPTS • A Database is a collection of related files containing records on specific entities. • Entities may be people, places or objects. • A Table has a specified number of columns, but can have any number of rows. A database table showing data stored on customers 11
  12. 12. DATABASE CONCEPTS • Field – represented by a column is an attribute or characteristic of an entity. A field name may be thought of as a question, and every cell within that field as a response to that question. • Record – represented by a row is one unit of information. Every cell on a given row is part of that row's record. • Table/file/relation - grid of columns and rows The vertical columns of a table are recognized by their name. 12
  13. 13. TYPES OF DBMS • There are four (4) main DBMS approaches     Hierarchical Network Relational Object Oriented 13
  14. 14. TYPES OF DBMS Hierarchical and Network DBMS • Called ‘‘navigational’’ approaches because of the way that programs have to ‘‘navigate’’ through hierarchies and networks of data to find the data they need. Both of these technologies were developed in the 1960s 1 • IBM’s Information Management System (IMS), a DBMS based on the hierarchical approach, was released in 1969. The hierarchical approach only supported 1 – M relationships, that is each child node could have only one parent. 2 3 4 5 6 14
  15. 15. TYPES OF DBMS • Hierarchical and Network DBMS  Were suitable only for mainframe computers.  An elegant solution to the redundancy/integration problem at the time that they were developed.  Were complex, difficult to work with in many respects.  Now often called ‘‘legacy systems,’’ some of them interestingly have survived to this very day for certain applications that require a lot of data and fast data response times. 15
  16. 16. TYPES OF DBMS • The relational database Invented by E. F. Codd at IBM in 1970. Became commercially viable in about 1980. Is the preferred DBMS approach. A relational database is a set of tables containing data fitted into predefined categories (attributes). 16
  17. 17. TYPES OF DBMS • The relational database  Each table (which is sometimes called a relation) contains one or more data categories in columns. Each row contains a unique instance of data for the categories defined by the columns.  For example, a typical business order entry database would include a table that described a customer with columns for name, address, phone number, and so forth. Another table would describe an order: product, customer, date, sales price, and so forth.  A user of the database could obtain a view of the database that 17
  18. 18. TYPES OF DBMS • Object-Oriented Approach  Allows the definition of objects, which are different from normal database objects.  Objects, in an object-oriented database, reference the ability to develop a product, then define and name it.  The object can then be referenced, or called later, as a unit without having to go into its complexities.  This is very similar to objects used in object-oriented programming. 18
  19. 19. SUMMARY • Data is a ubiquitous and important • A Database is a collection of related data • A DBMS is used to manage a database • A Database consists primarily of Tables • A Table consists of: Records (Rows in a table) • Attributes are columns in a table also called fields • There are four major types of DBMS Approaches 19
  20. 20. REFERENCES • Gillenson, Mark L.,2012, Fundamentals of Database Management Systems / Mark L. Gillenson.—2nd ed., John Wiley and sons inc • • • Object-relational_database.html 20