We are working on DW project. one of the phase of this process is to setup a replication from transactional db to staging db. I would like to know which type of replication we should implement and our requirement is to replicate only specific columns from a particular tables not entire table. We are using Sql 2008+. Please recommend and also replication setup steps .
Determination of what type of replication to use is really an art, based upon many factors. With what you have provided, it is hard to determine whether to use snapshot or transactional. With either, you can pick the fields that you want of a table with one exception, a primary key. Each table replicated must have a unique primary key and it must be replicated. In addition, I would want to know how much data are we talking about. How busy are the servers. The use of snapshots places additional strain on servers and network bandwidth. To help you with your endeavors, here is a link to a free e-book which has a lot of information, and should be able to answer all of your questions.
http://www.sqlservercentral.com/articles/books/101780/ Each type of replication has a purpose, and a place.
Replication is very flexible. You can certainly replicate just a subset of the database. Replication is not necessarily the best approach. It depends on how big that subset of the data is, how fast the data changes, and whether you want it to be constantly changing in your data warehouse or updated periodically.
I know you asked about replication and I think that both @DavidWimbush and @sjimmo have very valid answers however I'll throw this out there. Have you looked at using SSIS? Do you need the data real-time like? If you don't, SSIS is an excellent tool to load a data warehouse and/or move data. Not only can you load the data, you would be able to transform it in flight to meet your DW design thus potentially not landing the data twice. Once to staging and then again to the warehouse. Depending on your OLTP data design, after an initial load you could then just load the delta's on a schedule. Just a thought I'd throw out there as a potential alternative.