Chapter 1 Databases and Database Users Copyright 2011 Pearson Education Inc Publishing as Pearson Addison Wesley Chapter 1 Outline Introduction An Example Characteristics of the Database Approach Database Users Advantages of Using the DBMS Approach When Not to Use a DBMS Copyright 2011 Ramez Elmasri and Shamkant Navathe Introduction Database Collection of related data Known facts that can be recorded and that have implicit meaning Miniworld or universe of discourse UoD Represents some aspect of the real world Built for a specific purpose Copyright 2011 Ramez Elmasri and Shamkant Navathe Introduction cont d Example of a large commercial database Amazon com Database management system DBMS Collection of programs Enables users to create and maintain a database Defining a database Specify the data types structures and constraints of the data to be stored Copyright 2011 Ramez Elmasri and Shamkant Navathe Introduction cont d Meta data Database definition or descriptive information Stored by the DBMS in the form of a database catalog or dictionary Manipulating a database Query and update the database miniworld Generate reports Copyright 2011 Ramez Elmasri and Shamkant Navathe Introduction cont d Sharing a database Allow multiple users and programs to access the database simultaneously Application program Accesses database by sending queries to DBMS Query Causes some data to be retrieved Copyright 2011 Ramez Elmasri and Shamkant Navathe Introduction cont d Transaction May cause some data to be read and some data to be written into the database Maintain the database system Allow the system to evolve as requirements change over time Copyright 2011 Ramez Elmasri and Shamkant Navathe Copyright 2011 Ramez Elmasri and Shamkant Navathe An Example UNIVERSITY database Information concerning students courses and grades in a university environment Data records STUDENT COURSE SECTION GRADE REPORT PREREQUISITE Copyright 2011 Ramez Elmasri and Shamkant Navathe An Example cont d Specify structure of records of each file by specifying data type for each data element String of alphabetic characters Integer Etc Copyright 2011 Ramez Elmasri and Shamkant Navathe An Example cont d Construct UNIVERSITY database Store data to represent each student course section grade report and prerequisite as a record in appropriate file Relationships among the records Manipulation involves querying and updating Copyright 2011 Ramez Elmasri and Shamkant Navathe An Example cont d Examples of queries Retrieve the transcript List the names of students who took the section of the Database course offered in fall 2008 and their grades in that section List the prerequisites of the Database course Copyright 2011 Ramez Elmasri and Shamkant Navathe An Example cont d Examples of updates Change the class of Smith to sophomore Create a new section for the Database course for this semester Enter a grade of A for Smith in the Database section of last semester Copyright 2011 Ramez Elmasri and Shamkant Navathe An Example cont d Phases for designing a database Requirements specification and analysis Conceptual design Logical design Physical design Copyright 2011 Ramez Elmasri and Shamkant Navathe Copyright 2011 Ramez Elmasri and Shamkant Navathe Characteristics of the Database Approach Traditional file processing Each user defines and implements the files needed for a specific software application Database approach Single repository maintains data that is defined once and then accessed by various users Copyright 2011 Ramez Elmasri and Shamkant Navathe Characteristics of the Database Approach cont d Main characteristics of database approach Self describing nature of a database system Insulation between programs and data and data abstraction Support of multiple views of the data Sharing of data and multiuser transaction processing Copyright 2011 Ramez Elmasri and Shamkant Navathe Self Describing Nature of a Database System Database system contains complete definition of structure and constraints Meta data Describes structure of the database Database catalog used by DBMS software Database users who need information about database structure Copyright 2011 Ramez Elmasri and Shamkant Navathe Copyright 2011 Ramez Elmasri and Shamkant Navathe Insulation Between Programs and Data Program data independence Structure of data files is stored in DBMS catalog separately from access programs Copyright 2011 Ramez Elmasri and Shamkant Navathe Data Abstraction Data abstraction Allows program data independence and program operation independence Conceptual representation of data Does not include details of how data is stored or how operations are implemented Data model Type of data abstraction used to provide conceptual representation Copyright 2011 Ramez Elmasri and Shamkant Navathe Support of Multiple Views of the Data View Subset of the database Contains virtual data derived from the database files but is not explicitly stored Multiuser DBMS Users have a variety of distinct applications Must provide facilities for defining multiple views Copyright 2011 Ramez Elmasri and Shamkant Navathe Sharing of Data and Multiuser Transaction Processing Allow multiple users to access the database at the same time Concurrency control software Ensure that several users trying to update the same data do so in a controlled manner Result of the updates is correct Copyright 2011 Ramez Elmasri and Shamkant Navathe Sharing of Data and Multiuser Transaction Processing cont d Transaction Central to many database applications Executing program or process that includes one or more database Isolation property Each transaction appears to execute in isolation from other transactions Atomicity property Either all the database operations in a transaction are executed or none are Copyright 2011 Ramez Elmasri and Shamkant Navathe Database Users Database administrators DBA are responsible for Authorizing access to the database Coordinating and monitoring its use Acquiring software and hardware resources Database designers are responsible for Identifying the data to be stored Choosing appropriate structures to represent and store this data Copyright 2011 Ramez Elmasri and Shamkant Navathe Database Users cont d End users People whose jobs require access to the database Copyright 2011 Ramez Elmasri and Shamkant Navathe Database Users cont d System analysts Determine requirements of end users Application programmers Implement these specifications as programs Copyright 2011 Ramez Elmasri and