BA, SA, DA, and QA work together. As my experience BA and SA have more responsibilities during the project. They stay in touch with project manager in daily basis and DA and QA usually work for BA and SA. BA and SA job descriptions are almost same. They can do both job plus testing as well. Most of my team members title was Business System Analyst. Data analyst/QA jobs are easier if you have little bit knowledge about different phases of project and some testing tools like QC/ALM, QTP, defect tracking tools etc. If you know visual basic you can work on QTP easily. QA needs to communicate with BA/Developer frequently because they are the one who finds hidden bugs in the application. QA does thorough testing and at last BA does UAT testing and sends for production. Once it goes to production...it will be very costly for the company to re-work on same application because there is always projects line up one after another. I see most of the Project mangers are in tense.It is so difficult to work with someone who comes from desi consultancy. They come with 8 years of experience to become BA/SA and they know nothing.  There are different level of QA such as, Junior, senior, lead, test manager etc. I think it is better to start from QA/DA and BA later. Salary is almost same to all developer, BA and QA depends on their experience and Company. These days almost all company ask for automation experience for all QA even if you don't have to work on them.