Introduction to Database Management System.pptx
- 1. Introduction to Database Management System Dr. Yashoda M B Assistant Professor Department of Computer Science (UG) Kristu Jayanti College (Autonomous)
- 2. Introduction Database: A database is a collection of related data. Data: By data, we mean known facts that can be recorded and that have implicit meaning. For example, consider the names, telephone numbers, and addresses of the people you know. Address book Hard drive Excel DBMS: A database management system is a collection of programs that enables users to create and maintain a database
- 3. The DBMS is a general-purpose software system that facilitates the processes of defining, constructing, manipulating, and sharing databases among various users and applications. Defining a database involves specifying the data types, structures, and constraints of the data to be stored in the database. The database definition or descriptive information is also stored by the DBMS in the form of a database catalog or dictionary; it is called meta-data. Constructing the database is the process of storing the data on some storage medium that is controlled by the DBMS. Manipulating a database includes functions such as querying the database to retrieve specific data, updating the database to reflect changes, and generating reports from the data. Sharing a database allows multiple users and programs to access the database simultaneously
- 4. An application program accesses the database by sending queries or requests for data to the DBMS. A query typically causes some data to be retrieved. a transaction may cause some data to be read and some data to be written into the database. Other important functions provided by the DBMS include protecting the database and maintaining it over a long period of time. Protection includes system protection against hardware or software malfunction (or crashes) and security protection against unauthorized or malicious access. A typical large database may have a life cycle of many years, so the DBMS must be able to maintain the database system by allowing the system to evolve as requirements change over time.
- 5. Figure 1: A Simplified Database Environment
- 6. Characteristics of DBMS Self-describing nature of a database system Complete definition or description of the database structure and constraints This information is stored in DBMS catalog. The information stored in the catalog is called _____________ The catalog is used by the DBMS software and also by database users who need information about the database structure. For the example shown in Figure 1.2, the DBMS catalog will store the definitions of all the files shown.
- 9. Insulation between programs and data, and data abstraction In traditional file processing, the structure of data files is embedded in the application programs, so any changes to the structure of a file may require changing all programs that access that file. The structure of data files is stored in the DBMS catalog separately from the access programs. We call this property program-data independence. In some types of database systems, such as object-oriented and object- relational systems, users can define operations on data as part of the database definitions. User application programs can operate on the data by invoking these operations through their names and arguments, regardless of how the operations are implemented. This may be termed program-operation independence. The characteristic that allows program-data independence and program-operation independence is called data abstraction. A DBMS provides users with a conceptual representation of data that does not include many of the details of how the data is stored or how the operations are implemented. A data model is a type of data abstraction that is used to provide this conceptual representation
- 11. Support of multiple views of the data A database typically has many types of users, each of whom may require a 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 is not explicitly stored
- 12. Sharing of data and multiuser transaction processing A multiuser DBMS, as its name implies, must allow multiple users to access the database at the same time. The DBMS must include concurrency control software to ensure that several users trying to update the same data do so in a controlled manner so that the result of the updates is correct. For example, when several reservation agents try to assign a seat on an airline flight, the DBMS should ensure that each seat can be accessed by only one agent at a time for assignment to a passenger. These types of applications are generally called online transaction processing (OLTP) applications. The concept of a transaction has become central to many database applications. A transaction is an executing program or process that includes one or more database accesses, such as reading or updating of database records.