hi ashish,
the only way you can learn about datawarehouse is with experience when you are on the project, i am not sure of any institutes in Banglore, but if you try you can learn yourself it is not diffcult, the concept is very simple, you need to learn different tools, and all tools are more or less similar.
well for beginers, there wont be much offers, but if you really good at the subject you can fake the experience(sorry to say but so many do it). if you need any help or you have any questions regarding Data warehouse just post it here, i can help you as long as i can..
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well regarding the future of the DW, according to my expectation, the market should be good, as every company(in all domains) need a datawarehouse in the future to analyse thier business. and what ever the transaction systems in development now they will go for a datawarehouse sometime in the future.
all the best