which one has better job prospects-Computer Science/Electronics/Maths & Computing/Mining?

All the branches have good scope it totally depends on your interest. You should choose the branches according to your interest. If we compare all the branches then CSE is the most demading branch followed be ECE among students.

You can also check the scope from the given below link-

CSE

Computer science placements are excellent there are large service providers such as TCS, CTS, Wipro and Infosys. Apart from these service providers, large multinational companies such as Google, Microsoft, Facebook and Amazon hire students from reputed institutions such as IITs, BITs, NITs, CEG-Guindy etc.

Computer science professionals are paid very well all over the world, be it in India or abroad. However, salary varies greatly and is highly dependent on students academic profile and university reputation. Students from IITs tend to get a starting pay package that is significantly higher than students from lesser known institutions in India.

ECE

The average salary of an Electronics and Communication degree holder is between INR 3.5 lakh and INR 4.5 lakh per annum . Fresher candidates usually get a starting salary of INR 20,000 to INR 30,000 per month depending upon their interview performance and knowledge. The salary package offered to an IIT graduate is on higher side – the average salary is INR 10.55 lakh per annum and maximum is INR 25 lakh per annum .

Maths and computing

Mathematics & Computing Engineering is an amalgamation of mathematics with computer science and financial engineering. Covering the major areas in demand today, this course is of utmost value to the aspiring engineers.

On successful completion of the course, students can find a job in software industries, financial institutions and government organizations. The employment areas also cover Consulting Engineering firms, Pharmaceutical Industry, Telecom industry, Banks and Insurance companies and Government organizations as well. Top recruiters include companies like Microsoft, Mphasis, Amazon India, L & T Ltd., Avacor.

Mining

With the increase in concern for the environment and ecological system, the need for Mining engineering has also gained value.

As far as the compensation is concerned, a mining engineer earns around US Dollar 15250, or 10LPA in INR.
There are many public limited firms or government organization who offer facilities like housing, food, etc., over and above the salary package.

Good Luck!!