OracleByAjay

Oracle Freshers training , Cognizant - Calcutta Active Database An active Database is a database consisting of a set of triggers. These databases are very difficult to be maintained because of the complexity that arises in understanding the effect of these triggers. In such database, DBMS initially verifies whether the particular trigger specified in the statement that modifies the database is activated or not, prior to executing the statement. If the trigger is active then DBMS executes the condition part and then executes the action part only if the specified condition is evaluated to true. It is possible to activate more than one trigger within a single statement. In such situation, DBMS processes each of the trigger randomly. The execution of an action part of a trigger may either activate other triggers or the same trigger that Initialized this action. Such types of trigger that activates itself is called as ‘recursive trigger’. The DBMS executes such chains of trigger in some pre

Oracle training at Goldman Sachs, Banglore.     DATABASE MANAGEMENT SYSTEMS     UNIT II: Relational Model & Basic SQL   s: Relational Model: Introduction to relational model, concepts of domain, attribute, tuple, relation, importance of null values, constraints (Domain, Key constraints, integrity constraints) and their importance BASIC SQL: Simple Database schema, data types, table definitions (create, alter), different DML operations (insert, delete, update), basic SQL querying (select and project) using where clause, arithmetic & logical operations, SQL functions (Date and Time, Numeric, String conversion).   Objectives: After studying this unit, you will be able to: l     Describe Relational model l     Describe SQL and data types l     Explain the basic structures of SQL queries l     Know how to create tables l     Realise aggregate functions and null values   2.1    Introduction Relational Model was proposed