Introduction of oracle database

Introduction of oracle database

• 1.
  Introduction of oracledatabase
• 2.
   Oracle corporationhas come a long way to become the multinational technology company that it is today. Its rich history tracks its progress through the development and marketing of computer hardware systems, enterprise software and Oracle itself, the world renowned database technology.
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   Founding ofOracle.  In 1995 oracle became one of the first large software companies to report an internet strategy.  In 1977, Larry Ellison, Bob Miner, and Ed Oates started the consultancy Software Development Laboratories, which became Relational Software, Inc. (RSI). In 1983, RSI became Oracle Systems Corporation and then later Oracle Corporation.
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   Every organizationhas information that it must store and manage to meet its requirements.  An information system is a formal system for storing and processing information.  A database is an organized collection of information treated as a unit. The purpose of a database is to collect, store, and retrieve related information for use by database applications.
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   The relationalmodel is the basis for a relational database management system (RDBMS). Essentially, an RDBMS moves data into a database, stores the data, and retrieves it so that it can be manipulated by applications. An RDBMS distinguishes between the following types of operations:  Logical operations-An application specifies what content is required. For example, an application requests an employee name or adds an employee record to a table.  Physical operations- The RDBMSdetermines how things should be done and carries out the operation. For example, after an application queries a table, the database may use an index to find the requested rows, read the data into memory, and perform many other steps before returning a result to the user. The RDBMS stores and retrieves data so that physical operations are transparent to database applications.
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   Tables  Atable describes an entity such as employees. You define a table with a table name, such as employees, and set of columns. In general, you give each column a name, a data type, and a width when you create the table.  Indexes  An index is an optional data structure that you can create on one or more columns of a table. Indexes can increase the performance of data retrieval. When processing a request, the database can use available indexes to locate the requested rows efficiently. Indexes are useful when applications often query a specific row or range of rows.
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   Structured QueryLanguage (SQL)  SQL is a set-based declarative language that provides an interface to an RDBMS such as Oracle Database. In contrast to procedural languages such as C, which describe how things should be done, SQL is nonprocedural and describes what should be done. Users specify the result that they want (for example, the names of current employees), not how to derive it. SQL is the ANSI standard language for relational databases.
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   SELECT *FROM table_name;  SELECT first_name, last_name FROM employees;  SELECT * FROM Customers;  SELECT CustomerName,City FROM Customers;  SELECT DISTINCT Country FROM Customers;  SELECT Count(*) AS DistinctCountries FROM (SELECT DISTINCT Country FROM Custom ers);
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   Oracle DBAtraining in chennai  http://www.besanttechnologies.in/