Technology Questions

It enables SQL server to address diverse data sources like OLE DB similarly. It allows Remote server access and has the ability to issue distributed queries, updates, commands and transactions.

Immutable classes are Java classes whose objects can not be modified once created. Any modification in Immutable object result in new object. For example is String is immutable in Java. Mostly Immutable are also final in Java, in order to prevent sub class from overriding methods in Java which can compromise Immutability. You can achieve same functionality by making member as non final but private and not modifying them except in constructor.

OLTP stands for OnLine Transaction Processing. Applications that supports and manges transactions which involve high volumes of data are supported by OLTP system. OLTP is based on client-server architecture and supports transactions across networks.

OLAP stands for OnLine Analytical Processing. Business data analysis and complex calculations on low volumes of data are performed by OLAP. An insight of data coming from various resources can be gained by a user with the support of OLAP.

A package is a collection of related PL/SQL objects. The package contains a body and a specification. The package specification has the declaration which is public and can be used in the PL/SQL sub programs inside the package.

The package body holds the implementation of all the PL/SQL objects declared in the specification.

Example of a PL/SQL Package.

CREATE OR REPLACE PACKAGE emp_data AS 

PROCEDURE add_employee (

      ename VARCHAR2,

      job VARCHAR2,

      mgr NUMBER,

      sal NUMBER,

      deptno NUMBER);

END emp_actions;

CREATE OR REPLACE PACKAGE BODY emp_data AS 

PROCEDURE add_employee (

       ename VARCHAR2,

       job VARCHAR2,

       mgr NUMBER,

       sal NUMBER,

       deptno NUMBER) IS

BEGIN

         INSERT INTO emp VALUES (empno_seq.NEXTVAL, ename, job, mgr, SYSDATE, comm, deptno);

END add_employee;

END emp_data;

Advantages of  PL/SQL packages :

Packages are easier for application designing, encapsulating data, additional functionality and better performance. An application has various modules which can be placed in packages and handled easier.

Type 4  (JDBC Net pure Java Driver) is the fastest JDBC driver.  Type 1 and Type 3 drivers will be slower than Type 2 drivers (the database calls are make at least three translations versus two), and Type 4 drivers are the fastest (only one translation).

HashCode method return int value. So the Hash value is the int value returned by the hash function .

If you want to do equality check or want to use your object as key in HashMap, we must override hashcode and equals() method.

Only one column can exist per table that is attached with ROWGUIDCOL property. One can then use $ROWGUID instead of column name in select list.

A PHP Session persist the user information to be used later. For example, user name, password, shopping item details. The session is temporary and will be removed soon after the user has left the web site. The session can be persisted for long term usage on databases like MySQL. Each session is identified by a unique Id number for every visitor. The first step to use PHP session is to start the session. The starting session must precede the operations like HTML or the other.

The statement session_start() starts the PHP session and registers the user’s information on the server.