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Wednesday, December 28, 2011

PL-SQL Aptitude/ Interview Questions and Answers

PL-SQL Aptitude/ Interview Questions and Answers

  1. Describe the difference between a procedure, function and anonymous pl/sql block.
    Level: Low
    Expected answer : Candidate should mention use of DECLARE statement, a function must return a value while a procedure doesn't have to.

    2. What is a mutating table error and how can you get around it?
    Level: Intermediate
    Expected answer: This happens with triggers. It occurs because the trigger is trying to update a row it is currently using. The usual fix involves either use of views or temporary tables so the database is selecting from one while updating the other.

    3. Describe the use of %ROWTYPE and %TYPE in PL/SQL
    Level: Low
    Expected answer: %ROWTYPE allows you to associate a variable with an entire table row.
    The %TYPE associates a variable with a single column type.

    4. What packages (if any) has Oracle provided for use by developers?
    Expected answer: Oracle provides the DBMS_ series of packages. There are many
    which developers should be aware of such as DBMS_SQL, DBMS_PIPE, DBMS_TRANSACTION,
    DBMS_LOCK, DBMS_ALERT, DBMS_OUTPUT, DBMS_JOB, DBMS_UTILITY, DBMS_DDL, UTL_FILE. If they can mention a few of these and describe how they used them, even better. If they include the SQL routines provided by Oracle, great, but not really what was asked.

    5. Describe the use of PL/SQL tables
    Expected answer: PL/SQL tables are scalar arrays that can be referenced by a
    binary integer. They can be used to hold values for use in later queries
    or calculations. In Oracle 8 they will be able to be of the %ROWTYPE designation, or RECORD.

    6. When is a declare statement needed ?
    The DECLARE statement is used in PL/SQL anonymous blocks such as with stand alone, non-stored PL/SQL procedures. It must come first in a PL/SQL stand alone file if it is used.

    7. In what order should a open/fetch/loop set of commands in a PL/SQL block be implemented if you use the NOTFOUND cursor variable in the exit when statement? Why?
    Expected answer: OPEN then FETCH then LOOP followed by the exit when. If not specified in this order will result in the final return being done twice because of the way the %NOTFOUND is handled by PL/SQL.

    8. What are SQLCODE and SQLERRM and why are they important for PL/SQL developers?
    Expected answer: SQLCODE returns the value of the error number for the last error encountered. The SQLERRM returns the actual error message for the last error encountered. They can be used in exception handling to report, or, store in an error log table, the error that occurred in the code. These are especially useful for the WHEN OTHERS exception.

    9. How can you find within a PL/SQL block, if a cursor is open?
    Expected answer: Use the %ISOPEN cursor status variable.

    10. How can you generate debugging output from PL/SQL?
    Expected answer: Use the DBMS_OUTPUT package. Another possible method is to just use the SHOW ERROR command, but this only shows errors. The DBMS_OUTPUT package can be used to show intermediate results from loops and the status of variables as the procedure is executed. The new package UTL_FILE can
    also be used.

    11. What are the types of triggers?
    Expected Answer: There are 12 types of triggers in PL/SQL that consist of
    combinations of the BEFORE, AFTER, ROW, TABLE, INSERT, UPDATE, DELETE and
    ALL key words:
    BEFORE ALL ROW INSERT
    AFTER ALL ROW INSERT
    BEFORE INSERT
    AFTER INSERT etc.







Tuesday, December 27, 2011

Unix Directory Structure

Question: What is the standard directory structure on a UNIX computer?
Answer: The following is a generalized overview.
  • / — the slash / character alone denotes the root of the virtual filesystem tree.
    • /bin — stands for "binaries" and contains certain fundamental utilities, such as ls or cp, needed by all users.
    • /sbin — stands for "system (or "superuser") binaries" and contains fundamental utilities, such as init, usually needed to start, maintain and recover the system.
    • /etc — contains configuration files and system databases.
    • /dev — stands for "devices". Contains file representations of peripheral devices.
    • /dev/null — also known as the "bit bucket" or "black hole", this pseudo device discards all contents written to it, and is typically used to pipe away unwanted data.
    • /dev/random — this pseudo device returns pseudorandom numbers when read from.
    • /dev/urandom — similar to /dev/random, except it always returns (less cryptographically-strong) pseudorandom numbers, even if there is not enough entropy in the system noise available.
    • /home — contains the home directories for the users.
    • /mnt — contains filesystem mount points.
    • /lib — contains system libraries.
    • /root — the home directory for the superuser root.
    • /tmp — a place for temporary files. Many Unices clear this directory upon start up.
    • /usr — originally the directory holding user home directories, its use has changed, and it now holds executables, libraries, and shared resources that are not system critical, like the X Window System, KDE, Perl, etc.
    • /usr/bin — this directory stores all binary programs distributed with the operating system not residing in /bin, /sbin or (rarely) /etc.
    • /usr/include — /usr/include stores the development headers used throughout the system.
    • /usr/lib — stores the required libraries for executables within /usr or elsewhere.
    • /usr/local — resembles /usr, except that its subdirectories are used for additions not part of the operating system distribution, such as custom programs or files from a BSD Ports collection. Usually has subdirectories such as /usr/local/lib or /usr/local/bin.
    • /var — a short for "variable." A place for files that may change often.
    • /var/log — contains system log files.
    • /var/mail — the place where all the incoming mails are stored. The user can access his/her own mail only, unless he/she has admin rights.
    • /var/spool — spool directory; contains print jobs, mail spools and other queued tasks.
    • /var/tmp — A place for temporary files preserved between system reboots.
    • /proc — contains all processing data (Process information about a running operating system).
    • /opt — contains add-on software.
    • /media — default mount point for removable devices.
    • /srv — server data (data for services provided by system).
    • /boot — contains all the important files which are required for successful booting process.
    • /sys — contains information related to hardware.

Technology Articles/FAQs

Technology Articles/FAQs
The technological advances of the last decade have brought about hitherto unimagined changes in the way we go about our lives.

Technology Articles/FAQs

What is Technology?
The Oxford Dictionary defines technology as the application of scientific knowledge for practical purposes, especially in industry. In other words, it can be said that it is an effort to put in practice the knowledge of tools, techniques, crafts, and methods to find a solutions of a particular problem.
The word technology is derived from Greek meaning, "art, skill, craft", and logia meaning the discipline of or "study of-". The term is used generally or in context with particular fields like information technology, Industrial technology and others.
Technology enables people to adjust with their natural surroundings, in other words, it make their adjustment simples and hassle free. If a particular technology makes things complex rather than making it simple it can't survive for long. Right from invention of wheels to super computer and methods of natural cure to genetically engineered medicine, the whole efforts are streamlined to make human adaptation with nature simples smooth and hassle free.
Technology Tutorials:
This advancement in technology has opened new vistas for human being and information technology is spearheading this change. The age of messenger is passé, now we have invented a swifter messenger in the form of emails. We are living in the age where any information is just a click away. The Internet is acting as an information super highway that connects every destination, big and small. This advancement in technology has made life of peoples simple. We appreciate the role of technology, but we can?t get content as a lot is still left to be done.
  • GPS Technology
    Best information on GPS.
      
  • What is GPS?
    The technological advances of the last decade have brought about hitherto unimagined changes in the way we go about our lives.
      
  • How GPS Works
    GPS or Global Positioning System is a technology for locating a person or an object in three dimensional space anywhere on the Earth or in the surrounding orbit. GPS is a very important invention of our time on account of the many different possibilities it brings.
      
  • Benefits of GPS
    GPS or Global Positioning System was originally developed as a military navigation tool. However the technology has grown along with a sub set of supporting technologies to serve other requirements within consumer budgets.
      
  • GPS Tracking and its Applications
    GPS technology was originally developed for defense purposes and later brought to the consumer market as a navigation technology.
Networking
1.        What is OSI Layer?
The OSI Model is used to describe networks and network application. Different layers of OSI Model has described.  

1.        What is WiMaX?
What is WiMAX? Simply put WiMAX is, Worldwide Interoperability for Microwave Access, a technology standard that enables high speed wireless internet.
 
2.        Why WiMAX?
WiMAX is an acronym for Worldwide Interoperability for Microwave Access. It is an assortment of technical specifications called 802.16. The technology used in WiMAX enables wireless transmission of broadband internet over distances in the range of up to 50 km.
 
3.        Will WiMAX Replace DSL?
There has been a lot of hype about WiMAX as the next generation technology that will wipe out wired internet connectivity. The contention is that, it is far easier and more cost effective to set up transmission towers than continuously extend the cables for last mile connectivity.
 
4.        Will WiMAX Replace WiFi?
Enthusiasts of WiMAX are of the view that this powerful technology will soon overtake WiFi, which looks feeble. This need not be the case, as both can have their separate applications.
 
5.        Is WiMAX Safe?
WiMAX enabled devices emit radio frequency electromagnetic waves when in use. These waves have been part of our everyday life for decades now, in the use of devices such as radio, television and mobile phones.
  
6.        WiMAX Billing ChallengesImagine being able to access your emails and attend an urgent office conference while you are holidaying in a remote hill station of India! It is this kind of possibility that makes WiMAX an irresistible contestant to the title ?the technology of tomorrow.? WiMAX has finally made high speed wireless internet access a reality no matter where you are or whether you are on the move.
1.        Internate Telephone Services
VoIP or voice over internet Protocol is that technology which makes it possible to make phone calls through the internet. This technology is given many common names as internet phone service or digital phone service or broadband phone service.
    
2.        VoIP History
VoIP stands for Voice over Internet Protocol. This phenomenon has made a profound change in the world of telephone communications. The traditional method of making calls the landlines are being fats replaced by this technology that has taken the world by storm.
    
3.        VoIP- What is VoIP?This section introduces you with the VoIP technology and its benefits. VOIP is so beneficial that is saves hundreds or even thousand of dollars if used extensively. That is the reason behind VOIP Popularity. Many Companies are using VoIP for communication and saving thousands of dollars.
    
4.        VoIP Phones
List of VoIP Phones that you can use to make VoIP Phone calls.
  
5.        Complete Guide to Setup VoIP on Linux Machine
Voice Over IP is a new communication means that let you telephone with Internet at almost null cost. How this is possible, what systems are used, what is the standard, all that is covered by this tutorial.
  
6.        VoIP Software Phones
VoIP Software Phones are basically a software for making VoIP calls using computer. Software phones are usually less expensive and it offers a better options for Computer Telephony Integration (CTI). Find free VoIP Software Phones for you home and business.
    
7.        Free VoIP Gateways
Here you will find the list of Free VoIP Gatways that you can use to connect the VoIP network to your public telephone network (PSTN). In this way, you can make calls and receive them, from your PTSN, even if you are using an IP-based system, just like your traditional phone.
  
8.        Free VoIP Gatekeepers
Here you will find the list of widely used free Gatekeepers for your VoIP system. These Gatekeepers provide centralized call management functions such as user location, authentication, bandwidth management, address translation, etc. along with bandwidth management.
 
9.        Free VoIP Software Development Library
These VoIP Software Development Libraries are being used for the development of VoIP software.
  
10.     Free VoIP Proxy
Here are the list of Free VoIP Proxy that you can use with your VoIP System
1.        What is WiFi?
WiFi is a globally used wireless networking technology that uses the 802.11 standard. The term WiFi is an abbreviation of ?wireless fidelity?. The technology used in WiFi was developed in 1997 by the Institute of Electrical and Electronics Engineers (IEEE).
 
2.        Why WiFi?
WiFi, or Wireless Fidelity, is a technology standard developed in 1997 by the Institute of Electrical and Electronics Engineers (IEEE). WiFi is all about high speed wireless internet access.
  
3.        WiFi Internet
WiFi, the short form of Wireless Fidelity, is a technology that allows you to connect to the internet without a cabled network. WiFi technology uses the 802.11 standard developed by the Institute of Electrical and Electronics Engineers (IEEE) and commercialized by the WiFi Alliance.
  
4.        What is WiFi Phone?
A WiFi phone is a wireless device that gives you the dual benefits of wireless connectivity and the cost savings of VoIP. It can be used in any areas- hotspots- where WiFi connectivity is provided.
  
5.        How to Become WiFi Hotspot?
WiFi technology is one of the hottest and fastest spreading worldwide. More and more businesses and individuals are setting up WiFi hotspots. Here are a few useful tips for those who are considering a hotspot as a business tool.
  
6.        What is WiFi Finder?
A WiFi finder is a device used for locating wireless hotspots without actually turning on the laptop or PDA. WiFi finders are small, battery operated and portable. A WiFi finder typically detects a hotspot within a radius of 200 feet and also determines the strength of the signal.
 
7.        Security for Home WiFi Network
Security is a huge concern for anyone setting up a WiFi network, as anyone who is close enough to the hotspot can break into your system and access the information.
 
8.        Security for Public WiFi Network
Wi-Fi hotspots present a unique set of security problems, quite different from the security issues involved in home and office networks. These hotspots have unknown computers accessing them. And in this case, the very nature of a public hotspot demands that it broadcasts its SSID.
1.        What is HSDPA?
HSDPA is an acronym for High Speed Downlink Packet Access which is an advanced protocol for mobile telephone data transmission. HSDPA is an evolved form of W-CDMA (Wideband Code Division Multiple Access) technology. HSDPA promises to provide download speeds.
 
1.        Location Based Service (LBS)This is one of the most popular services based on a different navigation technologies provided by the mobile communication network.
  
2.        Basic Components & Functionality of LBSConsists of basic electronic instruments like mobile phone, smart phone, laptop and other personal digital devices (PDA) for accessing information.
 
3.        How does LBS work?Location based service (LBS) is the application that users use to locate its own position with the help of some basic components like mobile devices, mobile communication network, service provider like the Global Positioning Service (GPS), data and yellow pages for the service station.
  
4.        How is LBS useful?LBS is designed to provide valuable information to the users based on location or position.
  
5.        Application of LBS in Different FieldsThe popularity of location- based service makes it one of most essential and useful asset in almost all industries. However, its market is divided into various categories including navigation, emergency assistance, tracking, advertising, billing, management, games and leisure.
 
6.        Types of LBSLocation based service enables us to find the geographical location of a mobile device with its user and provide various services related to the location information.
  
7.        Relation between GIS and LBSTechnological advances like Geographical Information System (GIS) and all kinds of location-based services like GPS have brought tremendous change in the lifestyle of people especially the way we communicate.
 
8.        Location Based Service (LBS) in TourismIn a simple way if we have to define LBS then we can say that it is a service that determines where a mobile device and its user are geographically located and also acts as an information gateway for the user by providing various kinds of services.
  
9.        Pros and Cons of LBSLocation based service is one of the most important technological innovation in today's world as it contributes a lot in bringing changes in society.
  
10.      Security and Privacy Issues in Location Based Service (LBS)Location Based Service (LBS) is primarily based on user?s location to provide other value added services by means of a wireless device functioning through common cellular network or radio stations.
 
11.     Wi-Fi as a part of LBS
Wi-Fi Positioning System (WPS) uses wireless fidelity network instead of GPS or cell tower systems or location beacons to determine position.  
1.        What is Business Intelligence
Business Intelligence is a form of business management that takes business forward by the proper use of available information and data.
   
2.        History of Business IntelligenceThe 20 th and 21 st century are known as the information and technology (IT) age where everything depends on the availability of information and innovation of new technology.
  
3.        Business Intelligence ToolsWe have already discussed that Business Intelligence is a process to collect data and extract information and then analyzing them in developing new and innovative business ideas but the whole method is based on different computing tools.
 
4.        Business Intelligence Value ChainIn competitive marketplace it is vital for every business enterprise whether small or big to cope with the pace of the market growth. Intelligence is the ability to learn and understand new situations by updating yourself with current information.
  
5.        Business Intelligence in Decision MakingToday Business Intelligence is the primary tool to collect and analyze information for developing a successful business strategy.
 
6.        Privacy and Security Issues in BIWITH THE GROWTH of Business Intelligence market, the privacy and security issues are also growing concern over business community.
 
7.        The Future of Business IntelligenceInformation and communication technology has offered a single platform to world market irrespective of geographical position. Growing number of consumers with varied demand and expectation make it very difficult to conduct any kind of business.
    
8.        Business Intelligence in HealthcareTo make a profit driven business decision, every company depends on their strategic planning and decision-making ability and that depends on the kinds of information available and the ability to sort out the relevant ones for analysis.
 
9.        Business Intelligence in Insurance
Success in today's business world is defined by the ability to access sophisticated data and derive information that is now primary need to survive in the competitive market place. This is also true in insurance business that deals with rich and complex data structure and most of them are real-time.
Vehicle Tracking
1.        Vehicle Tracking TOC
VEHICLE TRACKING SYSTEM or Automatic Vehicle Location System (AVL) is now one of the most hot topic. Learn more about Vehicle Tracking here..
 
2.        Vehicle Tracking In India
Vehicle tracking system in India is mainly used in transport industry that keeps a real-time track of all vehicles in the fleet. The tracking system consists of GPS device that brings together GPS and GSM technology using tracking software.
 
1.        What is SCADA?
SCADA or Supervisory Control And Data Acquisition is a large scale control system for automated industrial processes like municipal water supplies, power generation, steel manufacturing, gas and oil pipelines etc. SCADA also has applications in large scale experimental facilities like those used in nuclear fusion.
  
2.        Why SCADA?
SCADA is an acronym that denotes Supervisory Control And Data Acquisition. SCADA is a control system with applications in managing large-scale, automated industrial operations. Factories and plants, water supply systems, nuclear and conventional power generator systems etc are a few examples.
    
3.        SCADA Programming
SCADA or Supervisory Control and Data Acquisition is a distributed measurement and control system for large-scale industrial automation. SCADA has applications in automated operations like chemical manufacturing and transport, supply systems and power generation.
     
4.        SCADA in Future
Elsewhere on this site we saw the fundamentals of SCADA and how it has emerged. In this article we will examine some of the challenges and applications that need to be met in order for SCADA to remain relevant to the new needs.