Unit 1.pptx
- 1. Unit 1 Database and Database system
- 2. What is Data? • Data is a collection of a distinct small unit of information. It can be used in a variety of forms like text, numbers, media, bytes, etc. it can be stored in pieces of paper or electronic memory, etc.
- 3. What is database? • The database is a collection of inter-related data which is used to retrieve, insert and delete the data efficiently. It is also used to organize the data in the form of a table, schema, views, and reports, etc. • For example: The college Database organizes the data about the admin, staff, students and faculty etc. • Using the database, you can easily retrieve, insert, and delete the information.
- 4. Characteristics of Database Approach The main characteristics of the database approach are: 1 Self-describing nature of a database system 2 Insulation between programs and data, and data abstraction 3 Support of multiple views of the data 4 Sharing of data and multiuser transaction processing
- 5. 1. Self-describing nature of a database system • A database system is referred to as self- describing because it not only contains the database itself, but also metadata which defines and describes the data and relationships between tables in the database.
- 6. 2. Insulation between programs and data, and data abstraction • In the file-based system, the structure of the data files is defined in the application programs so if a user wants to change the structure of a file, all the programs that access that file might need to be changed as well.
- 7. 3 Support of multiple views of the data • A database supports multiple views of data. A view is a subset of the database, which is defined and dedicated for particular users of the system. Multiple users in the system might have different views of the system. Each view might contain only the data of interest to a user or group of users.
- 8. 4 Sharing of data and multiuser transaction processing • Current database systems are designed for multiple users. That is, they allow many users to access the same database at the same time. This access is achieved through features called concurrency control strategies. These strategies ensure that the data accessed are always correct and that data integrity is maintained.
- 9. Database Management System • Database management system is a software which is used to manage the database. For example: MySQL, Oracle, etc are a very popular commercial database which is used in different applications. • DBMS provides an interface to perform various operations like database creation, storing data in it, updating data, creating a table in the database and a lot more. • It provides protection and security to the database. In the case of multiple users, it also maintains data consistency.
- 10. Advantages of DBMS • Controls database redundancy: It can control data redundancy because it stores all the data in one single database file and that recorded data is placed in the database. • Data sharing: In DBMS, the authorized users of an organization can share the data among multiple users. • Easily Maintenance: It can be easily maintainable due to the centralized nature of the database system. • Reduce time: It reduces development time and maintenance need. • Backup: It provides backup and recovery subsystems which create automatic backup of data from hardware and software failures and restores the data if required. • multiple user interface: It provides different types of user interfaces like graphical user interfaces, application program interfaces
- 11. Disadvantages of DBMS • Cost of Hardware and Software: It requires a high speed of data processor and large memory size to run DBMS software. • Size: It occupies a large space of disks and large memory to run them efficiently. • Complexity: Database system creates additional complexity and requirements. • Higher impact of failure: Failure is highly impacted the database because in most of the organization, all the data stored in a single database and if the database is damaged due to electric failure or database corruption then the data may be lost forever.
- 12. Classification/Types of DBMS Four Types of DBMS systems are: • Hierarchical database • Network database • Relational database • Object-Oriented database
- 13. Hierarchical database • In a Hierarchical database, model data is organized in a tree-like structure. Data is Stored Hierarchically (top down or bottom up) format. Data is represented using a parent- child relationship. In Hierarchical DBMS parent may have many children, but children have only one parent.
- 14. Network database • Network database management systems (Network DBMSs) are based on a network data model that allows each record to have multiple parents and multiple child records. A network database allows flexible relationship model between entities. • The model can be viewed as an upside-down tree where each member information is the branch linked to the owner, which is the bottom of the tree.
- 15. Relational Database • Relational DBMS is the most widely used DBMS model because it is one of the easiest. This model is based on normalizing data in the rows and columns of the tables. Relational model stored in fixed structures and manipulated using SQL.
- 16. Object-Oriented database • In Object-oriented Model data stored in the form of objects. The structure which is called classes which display data within it. It defines a database as a collection of objects which stores both data members values and operations.
- 17. Architecture of DBMS • A Database Architecture is a representation of DBMS design. It helps to design, develop, implement, and maintain the database management system. There are mainly three types of DBMS architecture: 1. One Tier Architecture (Single Tier Architecture) 2. Two Tier Architecture 3. Three Tier Architecture
- 18. 1. Single tier architecture • In this type of architecture, the database is readily available on the client machine, any request made by client doesn’t require a network connection to perform the action on the database. For example, lets say you want to fetch the records of employee from the database and the database is available on your computer system, so the request to fetch employee details will be done by your computer and the records will be fetched from the database by your computer as well.
- 19. 2. Two tier architecture
- 20. • In two-tier architecture, the Database system is present at the server machine and the DBMS application is present at the client machine, these two machines are connected with each other through a reliable network as shown in the above diagram. Whenever client machine makes a request to access the database present at server using a query language like sql, the server perform the request on the database and returns the result back to the client. The application connection interface such as JDBC, ODBC are used for the interaction between server and client.
- 21. 3. Three tier architecture
- 22. • In three-tier architecture, another layer is present between the client machine and server machine. In this architecture, the client application doesn’t communicate directly with the database systems present at the server machine, rather the client application communicates with server application and the server application internally communicates with the database system present at the server.
- 23. Types of database 1. Centralized database: When all data is store in a central data store house then, it is called centralized database .Every user at the different location access and uses the same central server to enter, edit, retrieve or modify the data, all the users use the same types of data structures. Major benefit of centralized database system are high security, minimum risk factor and easier maintainace and control.
- 24. 2. Distributed database When database is stored at more than one place or more than one computer , then it is called distributed database. Different user can use different DBMS, different data structures and each site controls its own data, security, logging and recovery mechanism and the computers in distributed database system communicate through various communication methods like high speed networks and telephone lines. Major benefits of this database system are transparency, easy data recovery ,improved performance and reliability.
- 25. Data models Data Model is a logical structure of Database. It describes the design of database to reflect entities, attributes, relationship among data, constrains etc. there are various type of data models 1. High level or conceptual data model 2. Low level or physical data model 3. Representation or implementation data model
- 26. High level or conceptual data model High level or conceptual data model provides concept that are understood by people who are not professionals. A conceptual data model provide concept such as entities, attributes and relationship. An entity is real word object such as employee or project. Attribute describes characteristics of entity. A relationship among two or more entities represented interaction or association among these entities.
- 27. Low level or physical data model low level data model provide concept that describes the details of how the data is store in the computer. concept provided by the low level data model are generally meant for computer specialist and no for end user.
- 28. Representation or implementation data model This type of data model is used to represent only the logical part of the database and does not represent the physical structure of the databases. The representational data model allows us to focus primarily, on the design part of the database. A popular representational model is Relational model. Most frequently used in development of commercial database and they includes a)Network model b) Hierarchical model c)Relational model
- 29. Define schema • The overall design of a database is called schema. • A database schema is the skeleton structure of the database. It represents the logical view of the entire database. • A schema contains schema objects like table, foreign key, primary key, views, columns, data types, stored procedure, etc. • It defines how the data is organized and how the relations among them are associated.
- 31. physical schema: The design of a database at physical level is called physical schema, how the data stored in blocks of storage is described at this level. logical schema: Design of database at logical level is called logical schema, programmers and database administrators work at this level, at this level data can be described as certain types of view schema: data records gets stored in data structures. Design of database at view level is called view schema. This generally describes end user interaction with database systems.
- 32. instance • The data stored in database at a particular moment of time is called instance of database. Database schema defines the variable declarations in tables that belong to a particular database; the value of these variables at a moment of time is called the instance of that database. OR • In short, at a particular moment the data stored in database is called the instance, that changes over time when we add or delete data from the database.
- 33. Database Administrator (DBA) A Database Administrator (DBA) is individual or person responsible for controlling, maintenance, coordinating, and operation of database management system. Managing, securing, and taking care of database system is prime responsibility. They are responsible and in charge for authorizing access to database, coordinating, capacity, planning, installation, and monitoring uses and for acquiring and gathering software and hardware resources as and when needed. Their role also varies from configuration, database design, migration, security, troubleshooting, backup, and data recovery.
- 34. What is Information? • Information is organized or classified data, which has some meaningful values for the receiver. Information is the processed data on which decisions and actions are based.