Computers & IT (Non-Engg)

Hi Srinivas,
Mentioned all three are in a good demand in their own field but the common factor is Skill, Expertise and Experience to be considered to become a successful professional.
Now, if I will about the overall situation then DevOps will be the future but here to answer your question precisely the availability of DBA professional either Oracle and SQL is less than other two. Also, if you begin your career in DBA then, later on, you may move to Big Data, Business Intelligence as a career.
Whereas, you will find a good competition in Networking because a number of candidates are more.
Development has many branches and you need to decide which path you need to follow. As per current market trends as well as in future demand Java, Angular Js, Node Js, Python, Jquery and Apex would help you a lot in Cloud computing back-end programming and IoT.

To learn Hadoop and to pass the certification exam, you may require some basic programming skills or understanding of the basic concepts of Java.
Hadoop is actually developed by Apache and it is based on the Java platform. So having some knowledge of Java would definitely help in understanding the concepts of Hadoop and also to follow the functionalities and terminologies that are associated with the Hadoop programming.
You may also learn some basic commands available with SQL as Hadoop mainly deals with the huge amount of data called Big Data and so having some SQL knowledge would help in processing and manipulation of the big data and do the required updates or modifications as and when required.
Working knowledge of Linux and its basic user commands would also be of great help.
Hadoop basically works on distributed computing model and it would follow the MapReduce algorithm to split the big data into various parts and put them on multiple servers available in a cluster.
So, you can very well go for doing the Hadoop certification exam if you have the necessary knowledge on Java, SQL and Linux so that you can understand the concepts and rules better while going through the Hadoop tutorials.
Any science/engineering graduate even commerce student is eligible for Hadoop but the course is not designed for freshers.