Database Management System Notes PDF

Database Management System Notes CHAPTER 1: Database and Database Users 1. Data Data means facts that can be recorded and that have implicit meaning. 2. Database Database is the collection of coherent, meaningful data organized in structured format. (eg. Univers...

Database Management System Notes CHAPTER 1: Database and Database Users 1. Data Data means facts that can be recorded and that have implicit meaning. 2. Database Database is the collection of coherent, meaningful data organized in structured format. (eg. University database in which info is kept on students – name, year etc. 3. Database Management System A DBMS is a collection of programs that enables users to create and maintain a database. A general-purpose software system that facilitates the process of defining, constructing, manipulating, and sharing databases among various users and application. (eg.MySQL, Microsoft Access) 4. Database System Integrated System of hardware, software, data, people and procedures. It defines and regulates the collection storage management and use of data within a database management. 5. Four Main Types of Actions involve in Database They are - i. Defining ii. Constructing iii. Manipulating iv. Sharing 6. Defining involves specific the data types, structures, and constraints of the data to be stored in the database. 7. Constructing Is the process of storing the data on some storage medium that is controlled by the DBMS. 8. Manipulating Includes functions such as querying the database to retrieve specific data, updating the database to reflect changes in the mini world and generating reports from the data. 9. Sharing Allows multiple user and programs to access the database simultaneously. 10.Metadata The database definition or descriptive information is stored by the DBMS in the form of catalog or dictionary and it is called meta-data. 11.Main Characteristics of Database Approach i. Self-describing nature of a database system ii. Insulation between programs and data and data abstraction iii. Support of multiple views of data iv. Sharing data and multiusers transaction processing 12.Self-describing nature of database system Database system contains not only database itself but also a complete definition or description of database structure and constraints stored in a DBMS catalog (contains information such as structure of each file, the type and storage format of each data item and various constraints on the data).  The information in the catalog is called meta-data. Data about data used by DBMS software and databases users to get info about database structure data definition separate from application programs 13.Program data independence DBMS access application programs written are independent of database structure i.e change in structure will not affect existing programs. 14.Data Abstraction The characteristics that allows program-data independence and program-operation independence is called data abstraction. It provides users with conceptual representation of data that does not include many details of how the data is stored or how the operations are implemented. 15.Data Model Data model is the type of data abstraction that is used to provide conceptual representation using logical constructs which may be easier to understand than actual computer storage concepts. It is not related to actual storage of data. 16.Support Multiple view of data Different may require different perspective or view of the database. A view may be a subset of the database or it may contain virtual data – that is derived from the database files but not is explicitly stored. 17.Sharing of data and multiuser transaction processing Database allows multiple users so data must be shared. Access to shared data must be monitored to ensure that multiple accesses do not corrupt the data (by using concurrency control software). Eg. Assign a seat on bus ticket online reservation system 18.Actors on the scene i. Database Administrators ii. Database Designers iii. End Users iv. System Analysts and Application Programmers 19.Database Administrators (DBA) Administers the database, DBMS and related software resources. They are responsible for authorizing access to the database, coordinating and managing use and acquiring software and hardware as needed. DBA is accountable security and poor system response time (assisted by staff) 20.Database Designers Design the structure of the database and also responsible for identifying the data to be stored and how to store it in the database. It also communicates with users to determine what data to be stored and what views to provide. 21.End Users People who access data through app software for querying, updating and generating reports. 21.Four Types of End users i. Casual end users ii. Naïve or parametric end users iii. Sophisticated end users iv. Standalone users 22. Casual End Users Occasionally access the database, but they may need different information each time. 23.Naïve Users Their main job function revolving around constantly querying and updating the database, using standard types of queries and updates called canned transactions. 24.Sophisticated end users Includes engineers, scientists and other professionals who familiarize themselves with the facilities of the DBMS in order to implement their own applications to meet their complex requirements. 25.Standalone Users Maintain personal database by using ready-made program packages that provide easy-to-use menu-based or graphics-based interfaces. 26.Programmers/Analysts Design and produce the application software for canned programs to be used by users. 27.Canned transactions Standard types of queries and updates which are carefully programmed and tested to assist naïve users in querying and updating the database. 28.Workers behind the scene Those who are associated with design, development and operation of the DBMS software and system environment. 29.DBMS system designers and implementers Design and implement the DBMS modules and interfaces as software package. (DBMS is complex software consist of may components, modules) 30.Tool Developers Design and implement tools. (Tools – software package that facilitate database modeling and design, database system design and improved performance.) 31.Operators and maintenance personnel Responsible for the actual running and maintenance of the hardware and software environment for the database system. 32.Deductive Database Systems Are to provide capabilities for defining deduction rules for inferencing new information from the stored database facts. 33..Advantages of using DBMS approach i. Controlling redundancy, ii. Restricting unauthorized access iii. Providing persistent storage for program objects iv. Database inferencing v. Representing complex relationships vi. Enforcing integrity constraints vii. Providing backup and recovery viii. Providing multiple user interface ix. Providing storage structures and search techniques for efficient query processing Controlling redundancy: redundancy means storing the same data multiple times. In DBMS, data is stored in a central place for use by many applications and users. Thus, a single storage location helps maintain consistency of data. Security : DBMS allows only authorized users to access certain data by permitting views to the particular user.  Persistent Storage : Unlike in programming language, DBMS data remains persistent after the program using it is complete. Database Inferencing : Some DBMS define rules for deriving data Multiple user interfaces : DBMS should provide a variety of user interfaces to fit the sophistication of the user. These include query languages for causal users, programming language interfaces for application programmers, forms and commands codes for parametric users and menu- driven interfaces and natural languages interfaces for standalone users. Representing complex relationships : DBMS represents related data and retrieves and updates related data efficiently. Enforcing integrity constraints : constraints can be defined that must hold in order for the data to be considered correct. Backup and Recovery – in case of system failure, recover to a consistent state using backup data. 34.When not to use DBMS i. Simple application which are for just one time use ii. Multi-user access is not needed iii. Stringent real-time requirements DBMS is costly