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Unit III: Database concepts and the Structured Query Language


                       9                               DATABASE CONCEPTS AND

                                                           THE STRUCTURED QUERY


                                                                                           LANGUAGE






              Chapter Outline


              9.1 Introducing DBMS                               9.2 Relational Data Model
              9.3 Structured Query Language (SQL)                9.4 Data Types
              9.5 SQL Statements and Functions                   9.6 DISTINCT clause
              9.7 ORDER By Clause                                9.8 BETWEEN Operator
              9.9 IN Operator                                    9.10 IS Operator
              9.11 LIKE Operator



            Introduction


            We have been dealing with data in all aspects of life much before computers' advent. Railways, healthcare systems,
            education, defence, and various businesses deal with vast amounts of data that need to be stored and managed
            efficiently. Since organisational decisions depend heavily on the timely availability of information, the companies felt
            the need for a system that could handle the data efficiently. Database Management System (DBMS) help store related
            data and manage it through application programs. Structured Query Language (SQL) is the most popular language for
            database creation and management. In this chapter, we shall study the basic concepts of DBMS.

            9.1 Introducing DBMS

            Data are raw facts. We often need to extract useful information from the data that forms the basis of decision-making.
            For example, consider a class of 50 students who have indicated their preference for the game they want to play out of
            the four games available: basketball, badminton, cricket, and table tennis. While individual choices are important, the
            school administration would like to know how many students want to play each game. Thus, summary information that
            cricket, badminton, basketball, and table tennis are the choices of 23, 10, 9, and 8 students, respectively, will be helpful
            to the school for planning purposes. Further, the preceding information concludes that cricket is the most popular game.
            Thus, we have obtained beneficial information by processing the raw data about individual student preferences. Fig 9.1
            illustrates the relationship between data and information.

                          0010110010110100101100
                          01111100101101001011111                                         Welcome
                          0010000010110100101100                                            to
                          00101111101101001011111                                     Informatics Practices
                          0010110010110000101100
                          00101100110101001011111


                                 Data                        Process                    Information
                                           Fig 9.1: Relationship between data and information

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