Advertisement

Introduction to database

Aug. 1, 2019
Advertisement

More Related Content

Advertisement

Introduction to database

  1. Introduction to DBMS Chapter-1
  2. Database Systems Database A collection of inter-related data that is organized in such a way that it can be easily accessed, managed and modified. DBMS It is a set of computer programs to access the data from a collection of related data which store, update and manage all those data Eg. MS Access, MySQL, MS SQL Server, Oracle, FoxPro, Dbase and so on Database System It is a collection of interrelated data and a set of programs to access 2
  3. DBMS A collection of general-purpose, application-independent programs providing services to ● define the structure of a database, i.e., data types and constraints that the data will have to satisfy ● manage the storage of data, safely for long periods of time, on some storage medium controlled by the DBMS ● manipulate a database, with client user interfaces to query the database to retrieve specific data, update the database to reflect changes in the world, generate reports from the data ● manage database usage, users with their access rights, performance optimization, sharing of data among several users, security from accidents or unauthorized use ● monitor and analyze database usage 3
  4. Database System Applications 1. Banking 2. Airlines 3. Universities 4. Telecommunications 5. Sales 6. Manufacturing and Inventory 7. Human resources 4
  5. Drawbacks of Using Traditional File Systems● Data Redundancy and Inconsistency ● Difficulty in accessing data ● Data Isolation ● Integrity problem ● Concurrent access anomalies ● Atomicity Problems ● Security Problems 5
  6. Drawbacks of Using Traditional File Systems 1. Data Redundancy and Inconsistency ○ Same information may be duplicated in different files ○ Redundancy leads to higher storage and access cost ○ Changes in one record may not be changed in other same records concurrently 2. Difficulty in accessing data ○ Conventional file systems do not allow to access only required data ○ Needs to access whole data even if only required few data causing in difficulty of access 6
  7. Drawbacks of Using Traditional File Systems 3. Data Isolation ○ Data is scattered in various files and files may be in different formats causing data isolation 4. Integrity problem ○ While storing data,, it needs to satisfy certain condition s ○ Eg. in bank, an account should have minimum balance 5. Concurrent access anomalies ○ Multiple users need to use and update data for overall performance and faster response ○ There is not any mechanism to support this in traditional file system 7
  8. Drawbacks of Using Traditional File Systems 6. Atomicity Problems ○ Any operations, to be atomic, should happen in its entirety or not at all ○ Atomic operations ensures that the system is in consistent state 7. Security Problems ○ Needs to reveal the whole information while requiring some information ○ No mechanism to support identification, authentication and authorization 8
  9. Advantages of DBMS ● No data Redundancy ● Data Consistency ● Sharing of data ● Enforcing data integrity ● Concurrency control ● Program-data Independence(Separation of data structure of database and application program) ● Data security ● Backup and Recovery 9
  10. Data Abstraction ● Hiding the complexity from the users through several level of abstraction ● To provide users with an abstract view of data 1. Physical level 2. logical/Conceptual level 3. View level 10
  11. Data Abstraction 11 Lowest level abstraction, high level complexity Higher level of abstraction, lower level of complexity
  12. Levels of Data Abstraction 1. Physical level ○ describes how records are stored into database ○ Also includes the database format and its storage like tree, hashing, indexing 2. Logical level ○ describes data stored in database, and the relationships among the data. ○ Database Administrators uses it for deciding what information to keep in the database 3. View level ○ Different users can view different data from the database according to their need. ○ application programs hide details of data types. ○ Views can also hide information (e.g., salary) for confidentiality and security. 12
  13. Schema and Instances Schema ● Overall design of the database ● Logical Structure of data in a database ● Analogous to type of a variable ● It may be physical schema, logical schema or sub-schema 1. Physical Schema: describes the database design at the physical level 2. Logical Schema: describes the database design at the logical level ● Physical schema is hidden beneath the logical schema and can be changed easily without affecting the application program. 13
  14. Schema and Instances Instances ○ Actual content of database at a particular point in time ○ Analogous to the values of a variable 14
  15. Data Independence ● Applications insulated from how data is structured and stored. 1. Logical data independence ○ Protection from changes in logical structure of data. 2. Physical data independence ○ Protection from changes in physical structure of data. 15
  16. Database Design ● Logical Design : Deciding on the database schema. ○ Business decision – What attributes should we record in the database? ○ Computer Science decision – What relation schemas should we have and how should the attributes be distributed among the various relation schemas? ● Physical Design : Deciding on the physical layout of the database 16
  17. Data Models ● Conceptual model for defining structure and behavior ○ structure: data types, relationships, constraints ○ behavior: basic operations for retrievals and updates ● A collection of tools for describing ○ Data ○ data relationships ○ data semantics ○ data constraints 17
  18. Data Models ● Relational model ● Entity-Relationship data model (mainly for database design) ● Object-based data models (Object-oriented and Object-relational) ● Other older models(Traditional data model): ○ Network model ○ Hierarchical model 18
  19. Relational Models ● Data is represented in the tabular form where each table has a number of rows and column. ○ Rows/Tuples/Records ○ Columns/Attributes/field 19 Tabular Data in a relational model
  20. Relational Models 20
  21. The Entity-Relationship Model • Models data as a collection of entities and relationships 1. Entity: a “thing” or “object” in the enterprise that is distinguishable from other objects e.g. Car, student, Customer 2. Attributes: defining the entities 3. Relationship: an association among several entities • Represented diagrammatically by an entity-relationship diagram: 21
  22. Other Data Models Object-Relational Data Models ● Extend the relational data model by including object orientation and constructs to deal with complex data types, including non-atomic values such as nested relations. ● Preserve relational foundations, in particular the declarative access to data, while extending modeling power. Hierarchical Model: ● Data organized in a tree structure. ● a hierarchy of parent and child data segments implying that a record can have repeating information, generally in the child data segments. Network Model: ● Data schema viewed as a graph in which object types are nodes and relationship types are arcs which is not restricted to being a hierarchy 22
  23. Database languages 1. DDL (Data Definition Language) ○ To specify the database schema(CREATE, ALTER, DROP) 2. DML (Data Manipulation Language) ○ To express the database queries and updates(SELECT, INSERT, DELETE, UPDATE) 3. DCL (Data Control Language) ○ To control the level of access that users have on database objects. 4. TCL (Transaction Control Language) ○ To allow users to control and manage transactions 23
  24. Database Users ● Users are differentiated by the way they expect to interact with the system 1. Application programmers ○ interact with system through DML calls 2. Sophisticated users ○ form requests in a database query language 3. Specialized users ○ write specialized database applications that do not fit into the traditional data processing framework 4. Naïve users ○ use one of the permanent application programs that have been written previously eg, people accessing database over the web, bank tellers, clerical staff 24
  25. Database Administrator ● Coordinates all the activities of the database system; the database administrator has a good understanding of the enterprise’s information resources and needs. ● Database administrator's duties include: ○ Schema definition ○ Storage structure and access method definition ○ Schema and physical organization modification ○ Granting user authority to access the database ○ Specifying integrity constraints ○ Acting as liaison with users ○ Monitoring performance and responding to changes in requirements 25
  26. Database Application Architectures 26
  27. Overall Database System Structure 27
Advertisement