29-10-2012, 03:50 PM
ORACLE
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Data Base Management System (DBMS)
Data
Database
Data Base Management System:-
Manage the whole data in perfect manner for following reasons:
User can search information easily
User can insert data easily in order
Updating easily
Deleting information easily
Advantage of DBMS
1. It reduces data redundancy.
2. It restricted unauthorized access.
3. It facilitates sharing of data.
4. It provides to describe backup & recovery.
SQL
SQL (Structure Query Language)
It is relational database language that enables you to create and operate on relational database.
Feature of SQL
It is a non procedural language.
It is a case insensitive language.
Both an ANSI and ISO standard
Types of commands:
Data Definition Language (DDL) : Create, Alter, Drop, Rename, Truncate
Data Manipulation Language (DML): Insert, Delete, Update, Select
Transaction Control(TCL): Commit, Rollback
Data Control Language (DCL): Grant, Revoke
LIMITATION OF SQL
No Procedure capabilities
Time consuming Processing
No Error Handling
Physical Structures
Datafiles (*.dbf)
The datafiles contain all the database data. The data of logical database structures, such as tables and indexes, is physically stored in the datafiles allocated for a database.
Control Files (*.ctl)
Every Oracle database has a control file. A control file contains entries that specify the physical structure of the database such as Database name and the Names and locations of datafiles and redo log files.
Redo Log Files (*.log)
The primary function of the redo log is to record all changes made to data. If a failure prevents modified data from being permanently written to the datafiles, then the changes can be obtained from the redo log, so work is never lost.