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Dbms slides
- 1. APPLICATIONS FILESYSTEM VIEW OF DATA QUERY PROCESSOR DATABASE USERS AND ADMINISTRATORS DATA LANGUAGES TRANSACTION MANAGEMENT STORAGE MANAGER DATA MODELS
- 2. APPLICATION a) BANKING: For customer ,informaion,account,and loans, and transaction. b) Airline: For reservation and schedule information. Airline were among the first to use database in a geographically distributed manner terminals situated around the world accessed the central database system through phone lines and other data network. c) Universities: For students information, course registration, and grades. d) Credits card transaction: For purchases on credits cards and generation of monthly statements. e) Sales: For customer, product, and purchase information. f) Human resources: For information about employees, salaries, payroll taxes and benefits, and for generation of paychecks.
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- 4. VIEW OF DATA 1.DATA ABSTRACTION • Physical Level: The lowest level of abstraction describes how the data are actually stored. • Logical Level: The next –higher level of abstraction describes what data are actually stored in the database, and what relationship exist among those data. • View Level: The highest level of abstraction describes only part of the entire database.
- 5. View level View 1 View 2 View n Logical level Physical level (The three levels of data abstraction)
- 6. INSTANCES AND SCHEMAS:The collection of information stored in the database at a particular moment is called an instance of the database. The overall design of the database is called the database schema.
- 7. QUERY PROCESSOR The query processor components includes: • DDL interpreter: Which interprets DDL statements and records the definitions in the data dictionary. • DML: Compiler which translates DML statements in a query language into an evaluation plan consisting of low- Level instructions that the evaluation engine understands. • Query evaluation engine: Which executes low-level instruction generates by the DML compiler.
- 8. Database Users and Administrators • Database users and user interfaces Naive Users Application Programmers Sophisticated Users Online analytical processing(ONLP) Specialized Users
- 9. • Database Administrator Schema definition Storage structure and access-method definition Schema and physical-organization modification Granting of authorization for data access Routine maintenance
- 10. DATA LANGUAGES The database provides a data definition Language to specify the database schema and a data Manipulation language to express database queries and updates. • DATA-DEFINITION LANGUAGE • DATA-MANIPULATION
- 11. DATA-DEFINITION LANGUAGE(DDL): We specify a database schema by a set of definition expressed by a special language called a Data-Definition Language. For instance, the following statement in the SQL language defines the account table: e.g. create table account(account-number char (10),balance integer) Execution of the above DDL statement create the account table. In addition, it updates a special set of tables called the DATA DICTIONARY or DATA DIRECTORY
- 12. DATA-MANIPULATION LANGUAGE: Data manipulationis: • The retrieval of information stored in the database. • The insertion of new information into the database. • The deletion of information from the database. • The modification of information stored in the database.
- 13. A data-manipulation language(DML)is a language that enables users to access or manipulate data as organized by the appropriate data model. There are basically two types : • Procedural DMLs • Declarative DMLs The query in the SQL language finds the name of the customer whose customer-id is 1999: e.g. Select customer.customer-name from customer where customer.customer-id=1999
- 14. TRANSACTION MANAGEMENT A transaction is a collection of operations that performs a single logical function in a database application. Each transaction is a unit of both atomicity and consistency . Thus, we require that transaction do not violate any database-consistency constraints. That is, if the database was consistent when a transaction started, the database must be consistent when the transaction successfully terminates.
- 15. STORAGE MANAGER A storage is a program module that provides the interface between the low-level data stored in the database and the application program and queries submitted to the system. The storage manager . The storage manager is responsible for the interaction with the file manager . The row data are stored on the disk using the file system, which is usually provided by a conventional operating system. The storage manager translates the various DML statements into low-level file-system commands. Thus, the storage manager is responsible for storing, retrieving and updating in the database.