Unit-I mech for studendts for btech .ppt
- 1. 1 Introduction to Database Management System
- 2. 2 DBMS File System DBMS is a collection of data. In DBMS, the user is not required to write the procedures. File system is a collection of data. In this system, the user has to write the procedures for managing the database. DBMS gives an abstract view of data that hides the details. File system provides the detail of the data representation and storage of data. DBMS provides a crash recovery mechanism, i.e., DBMS protects the user from the system failure. File system doesn't have a crash mechanism, i.e., if the system crashes while entering some data, then the content of the file will lost. DBMS provides a good protection mechanism. It is very difficult to protect a file under the file system. DBMS contains a wide variety of sophisticated techniques to store and retrieve the data. File system can't efficiently store and retrieve the data. DBMS takes care of Concurrent access of data using some form of locking. In the File system, concurrent access has many problems like redirecting the file while other deleting some information or updating some information.
- 4. PURPOSE OF DATABASE SYSTEM 4 • Database : It is the collection of interrelated and meaningful data. • Database Management System(DBMS) : • DBMS contains information about a particular enterprise • Collection of interrelated data • Set of programs to access the data • An environment that is both convenient and efficient to use • Goal of DBMS : The primary goal of DBMS is to provide a way to store and retrieve database information that is both convenient and efficient.
- 5. PURPOSE OF DATABASE SYSTEM 5 • Characteristics of DBMS : • It provides secure and survivable medium for storage and retrieval of data • It deals with management of data. • Defining structures for storing information • Providing mechanism for the manipulation of information • The system must ensure the safety of information stored , despite system crashes. • The data can be shared among several users and it is persistent.
- 6. PURPOSE OF DATABASE SYSTEM 6 Database System Applications : Banking : For Account, Loan and Customer information Airlines : For reservations and Schedule information Universities : For Student information , Regulation and Academic activities Credit Card Transactions : For purchases on credit cards and generation of monthly statements. Telecommunications : For keeping records of calls, generating monthly bill, maintaining balances on prepaid calling cards and storing information on the communication networks. Finance : For storing information about holdings, sales and purchases of financial instruments such as stocks and bonds
- 7. PURPOSE OF DATABASE SYSTEM 7 • Sales : For customer, product, and purchase information • Manufacturing : For tracking production of items in factories, inventory and ordering of items • Human Resources : For information about employees, salaries, payroll taxes and benefits. • Multimedia Databases : For storage and archival of Audio and Video files in online applications • Web databases : For keeping track of several web pages • Data Mining : For discovery of new knowledge
- 8. Database System Verses File Systems 8 • The information can be either a conventional file processing system or a database system. • In conventional file processing system, each and every subsystem of information system will have its own set of files and it leads to duplication. • But in DBMS, there is a single centralized database which minimizes the data redundancy of data to a greater extent.
- 9. PURPOSE OF DATABASE SYSTEM 9 • Database : It is the collection of interrelated and meaningful data. • Database Management System(DBMS) : • DBMS contains information about a particular enterprise • Collection of interrelated data • Set of programs to access the data • An environment that is both convenient and efficient to use • Goal of DBMS : The primary goal of DBMS is to provide a way to store and retrieve database information that is both convenient and efficient.
- 10. PURPOSE OF DATABASE SYSTEM 10 • Characteristics of DBMS : • It provides secure and survivable medium for storage and retrieval of data • It deals with management of data. • Defining structures for storing information • Providing mechanism for the manipulation of information • The system must ensure the safety of information stored , despite system crashes. • The data can be shared among several users and it is persistent.
- 11. PURPOSE OF DATABASE SYSTEM 11 Database System Applications : Banking : For Account, Loan and Customer information Airlines : For reservations and Schedule information Universities : For Student information , Regulation and Academic activities Credit Card Transactions : For purchases on credit cards and generation of monthly statements. Telecommunications : For keeping records of calls, generating monthly bill, maintaining balances on prepaid calling cards and storing information on the communication networks. Finance : For storing information about holdings, sales and purchases of financial instruments such as stocks and bonds
- 12. PURPOSE OF DATABASE SYSTEM 12 • Sales : For customer, product, and purchase information • Manufacturing : For tracking production of items in factories, inventory and ordering of items • Human Resources : For information about employees, salaries, payroll taxes and benefits. • Multimedia Databases : For storage and archival of Audio and Video files in online applications • Web databases : For keeping track of several web pages • Data Mining : For discovery of new knowledge
- 13. Database System Verses File Systems 13 • The information can be either a conventional file processing system or a database system. • In conventional file processing system, each and every subsystem of information system will have its own set of files and it leads to duplication. • But in DBMS, there is a single centralized database which minimizes the data redundancy of data to a greater extent.
- 14. ADVANTAGES OF DBMS 14 • Redundancy can be reduced • Inconsistency can be avoided • Data can be shared • Standards can be enforced • Security restrictions can be applied • Integrity can be maintained • Conflicting requirements can be balanced
- 15. DIS ADVANTAGES OF DBMS 15 • Complexity and Size • Additional hardware Cost • Cost of conversion • Performance • High impact of failure
- 16. DML 16 • Deals with • The insertion of new information into database. • The retrieval of information stored in the database • The deletion of information from the database • The modification of information in the database
- 17. DML COMMANDS 17
- 18. DML COMMANDS 18
- 19. DML COMMANDS 19 • Two types of DML : • Procedural DML : Require a user to specify what data are needed and how to get those data. E.g. Relational Algebra • Non Procedural DML : Require a user to specify what data are needed without specifying how to get those data. E.g. Tuple Relational Calculus • Query Language : The portion of DML that involves information retrieval is called query language. A query is statement requesting the retrieval of information . • E.g Select statement is the example of query.
- 21. DB ARCHITECTURE 21 • A database system is partitioned into modules that deal with each of the responsibilities of the overall system. • The main functional components of database system are : • Storage Manager : It which handles the storage space required for database manager. • Query Processor :It helps the database system simplify and facilitate access to data.
- 23. DB ARCHITECTURE 23 • Storage Manager : • Since the storage space for corporate databases ranges in the size from hundreds of gigabytes to terabytes of data, the main memory cannot handle such large amount of data and hence disk can be used.
- 24. DB ARCHITECTURE 24 • Functions • It is the program module that provides the interface between the low-level data stored in database and application programs and queries submitted to the system. • It translates the various DML statements into low-level system commands. • It is responsible for storing, retrieving and updating the data.
- 25. DB ARCHITECTURE 25 • Components • Authorization and Integrity Manager : Performs the test for ensuring Integrity constraint and authority of user. • Transaction Manager : Ensures that database remains in a consistent state despite system failure, and that concurrent transaction execution proceed without conflicting. • File Manager : It manages the allocation of space on the disk storage and the data structures used to represent information stored on the disk. • Buffer Manager : It is responsible for fetching data from disk storage into main memory and deciding what data to cache in main memory. It enables the database to handle data sizes that are larger than the size of main memory.
- 26. DB ARCHITECTURE 26 • Data Structures used by the Storage Manager • Data Files : It store the database itself • Data Dictionary : It stores the metadata about the structure of the database, in particular the schema of the database. Metadata means data about the data. • Indices : It provide fast access to data items that hold particular values.
- 27. DB ARCHITECTURE 27 • Query Processor : • DDL Interpreter : It interprets DDL statement and records the definition in data dictionary. • DML Compiler : It translates the DML statement in query language into an evaluation plan consisting of low-level instructions that the query evaluation engine understands. It performs the query optimization for finding the lowest cost evaluation plan. • Query Evaluation Engine : It executes low-level instructions generated by the DML compiler.
- 28. DB ARCHITECTURE 28 • DATABASE USERS : • There are three types of database-system users, differentiated by the way they expect to interact with the system. • Naive Users : They are unsophisticated users who interact with the system by invoking one of application programs that have been written previously. These users interact with the system using forms interface.
- 29. DB ARCHITECTURE 29 • Application Programmers : They are computer professionals who write application programs. They can choose from many tools to develop user interfaces. • Sophisticated Users : They interact with the system without writing programs. They form their requests in database query language. As analyst, they use Online Analytical Processing(OLAP) tool to analyze the statistical data and use Data Mining tools for generating certain kinds of patterns in data.
- 30. DB ARCHITECTURE 30 • DATABASE ADMINISTRATOR (DBA) • DBA is a person one who has central control of both the data and programs that access those data. • The functions of DBA include : • Schema Definition • Storage structures and access-method definition • Schema and Physical organization modification • Granting of authorization for data access • Routine Maintenance Periodic backup, • upgrading disk space as required. • Monitoring
- 31. DATA MODELS 31 • A collection of conceptual tools for describing • Data • Data relationships • Data semantics • Data constraints • Data model provides a way to describe the logical structure of database. • Data models define how data is connected to each other and how they are processed and stored inside the system.
- 32. DATA MODELS 32 • Types of data model : • Relational model • Entity-Relationship data model (mainly for database design) • Object-based data models (Object-oriented and Object-relational) • Semi-structured data model (XML)- Semi structured data model is a self describing data model • Other older models: • Network model • Hierarchical model
- 33. DATA MODELS 33 • The Relational Model • It consists of collection of tables which stores data and represents relationship among the data. • Table is called as relation. • Rows of table are called as tuples and columns of table are called as field or attribute. The describing properties of table are called attributes. • The set of permitted values of attribute are called as domain.
- 34. DATA MODELS 34
- 35. DATA MODELS 35 • Advantages – Structural independence – Improved conceptual simplicity – Easier database design, implementation, management, and use – Ad hoc query capability – Powerful database management system • Disadvantages – Substantial hardware and system software overhead – Can facilitate poor design and implementation – May promote “islands of information” problems
- 36. DATA MODELS 36 • The Entity Relationship Model(ER model) • This model is popular for high level database design, mainly used to represent entities and relationships exists between entities. • Entity : a ‘thing’ or ‘object’ in the real world that is distinguishable from all other objects. E.g. Each student in a college is an entity. • Relationship : used to provide association between two or more entities
- 37. DATA MODELS 37 • This model represents overall logical structure of a database • It is an aid for database design • It is easy to visualize and understand
- 38. DATA MODELS 38
- 39. DATA MODELS 39 • Advantages – Exceptional conceptual simplicity – Visual representation – Effective communication tool – Integrated with the relational data model • Disadvantages – Limited constraint representation – Limited relationship representation – No data manipulation language – Loss of information content
- 40. DATA MODELS 40 • Object-based data models (Object-oriented and Object-relational) • Models both data and their relationships in a single structure known as an object. • Object: abstraction of a real-world entity • Attributes describe the properties of an object • Objects that share similar characteristics are grouped in classes. • Includes information about relationships between facts within object and relationships with other objects. • Classes are organized in a class hierarchy • Inheritance is the ability of an object within the class hierarchy to inherit the attributes and methods of classes above it
- 41. DATA MODELS 41 • The object oriented data model extends the definition of an entity to include, not only the attributes that describe the state of the object but also the actions that are associated with the object, that is, its behavior.
- 42. DATA MODELS 42 • Advantages -Adds semantic content -Reusability (inheritance, polymorphism) -Support for schema evolution -Improved performance • Disadvantages -Lack of universal data model -Lack of experience -Complex
- 43. DATA MODELS 43 • Semi-structured data model (XML) : • Permits specification of data where individual data items of same type may have different sets of attributes. • The semi-structured model is a database model where there is no separation between the data and the schema, and the amount of structure used depends on the purpose.
- 44. DATA MODELS 44 • Advantages: • It can represent the information of some data sources that cannot be constrained by schema. • It provides a flexible format for data exchange between different types of databases. • It can be helpful to view structured data as semi-structured (for browsing purposes). • The schema can easily be changed. • The data transfer format may be portable.