CSC 426 Chapter 01, Fall 2011

Chapter 1 Introduction to Databases  Introduction  An Example  Characteristics of the Database Approach  Actors on the Scene  Workers behind the Scene  Advantages of Using the DBMS Approach  A Brief History of Database Applications  When Not to Use a DBMS Chapter 1 Outline  Traditional database applications ◦ Store textual or numeric information  Multimedia databases ◦ Store images, audio clips, and video streams digitally  Geographic information systems (GIS) ◦ Store and analyze maps, weather data, and satellite images Overview  Data warehouses and online analytical processing (OLAP) systems ◦ Extract and analyze useful business information from very large databases ◦ Support decision making  Real-time and active database technology ◦ Control industrial and manufacturing processes Overview (cont'd.)  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 ◦ Logically coherent collection of data with inherent meaning ◦ Built for a specific purpose Introduction  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 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 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 Introduction (cont'd.)  Transaction ◦ May cause some data to be read and some data to be written into the database  Protection includes: ◦ System protection ◦ Security protection  Maintain the database system ◦ Allow the system to evolve as requirements change over time Introduction (cont'd.)  UNIVERSITY database ◦ Information concerning students, courses, and grades in a university environment  Data records ◦ STUDENT ◦ COURSE ◦ SECTION ◦ GRADE_REPORT ◦ PREREQUISITE An Example  Specify structure of records of each file by specifying data type for each data element ◦ String of alphabetic characters ◦ Integer ◦ Etc. 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 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 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 An Example (cont'd.)  Phases for designing a database: ◦ Requirements specification and analysis ◦ Conceptual design ◦ Logical design ◦ Physical design An Example (cont'd.)  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 Characteristics of the Database Approach  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 Characteristics of the Database Approach (cont'd.)  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 Self-Describing Nature of a Database System  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 Support of Multiple Views of the Data  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  Online transaction processing (OLTP) application Sharing of Data and Multiuser Transaction Processing  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 Actors on the Scene  End users ◦ People whose jobs require access to the database ◦ Types • Casual end users • Naive or parametric end users • Sophisticated end users • Standalone users Actors on the Scene (cont'd.)  System analysts ◦ Determine requirements of end users  Application programmers ◦ Implement these specifications as programs Actors on the Scene (cont'd.)  DBMS system designers and implementers ◦ Design and implement the DBMS modules and interfaces as a software package  Tool developers ◦ Design and implement tools  Operators and maintenance personnel ◦ Responsible for running and maintenance of hardware and software environment for database system Workers behind the Scene  Controlling redundancy ◦ Data normalization ◦ Denormalization • Sometimes necessary to use controlled redundancy to improve the performance of queries  Restricting unauthorized access ◦ Security and authorization subsystem ◦ Privileged software Advantages of Using the DBMS Approach  Providing backup and recovery ◦ Backup and recovery subsystem of the DBMS is responsible for recovery  Providing multiple user interfaces ◦ Graphical user interfaces (GUIs)  Representing complex relationships among data ◦ May include numerous varieties of data that are interrelated in many ways Advantages of Using the DBMS Approach (cont'd.)  Enforcing integrity constraints ◦ Referential integrity constraint • Every section record must be related to a course record ◦ Key or uniqueness constraint • Every course record must have a unique value for Course_number Advantages of Using the DBMS Approach (cont'd.)  Additional implications of using the database approach ◦ Reduced application development time ◦ Flexibility ◦ Availability of up-to-date information ◦ Economies of scale Advantages of Using the DBMS Approach (cont'd.)  More desirable to use regular files for: ◦ Simple, well-defined database applications not expected to change at all ◦ Stringent, real-time requirements that may not be met because of DBMS overhead ◦ Embedded systems with limited storage capacity ◦ No multiple-user access to data When Not to Use a DBMS  Database ◦ Collection of related data (recorded facts)  DBMS ◦ Generalized software package for implementing and maintaining a computerized database  Several categories of database users Summary