Oracle Certification Questions

An index is an optional structure associated with a table to have direct access to rows, which can be created to increase the performance of data retrieval. Index can be created on one or more columns of a table.

Local :

Only available to the current Db connection for current user and are cleared when connection is closed.

Multiple users can’t share a local temporary table.

Global:

Available to any connection once created. They are cleared when the last connection is closed.

Can be shared by multiple user sessions

Alter database backup control file to trace

MAX command is used to return maximum value from result setMAX 

Data is organized in the form of row and columns, thus it is in tabular structure.

SQL statements are broadly classified into three. They are

1. DDL – Data Definition Language

DDL is used to define the structure that holds the data. For example, Create, Alter, Drop and Truncate table.

2. DML – Data Manipulation Language

DML is used for manipulation of the data itself. Typical operations are Insert, Delete, Update and retrieving the data from the table. The Select statement is considered as a limited version of the DML, since it can't change the data in the database. But it can perform operations on data retrieved from the DBMS, before the results are returned to the calling function.

3. DCL – Data Control Language

DCL is used to control the visibility of data like granting database access and set privileges to create tables, etc. Example - Grant, Revoke access permission to the user to access data in the database.

XPath is an expressions to select a xml node in an XML document.

It allows the navigation on the XML document to the straight to the element where we need to reach and access the attributes.