I am planning to buy a notebook. My concern is: I will use it for .NET or other language related purposes and want to know whether it fully supports .NET / other software like Oracle etc.
For software like Oracle your limitations will be licensing issues and operating system issues as well as hardware issues.
For example, does Oracle allow you to install it on a non-server Windows OS?
Do you have enough disk space on a notebook to install the database that you want to use?
Also, since a notebook only has one hard drive and usually a pretty slow one, you will have many differences in query performance if you're trying to develop against a sample database. A query design that works very well with 8 CPU cores and a SAN might crawl when run on 2 CPU cores and a single drive. Yet, designing a query to work on the notebook might leave a lot of potential performance behind.
The other danger with today's notebooks is that the hard drive will be an SSD. This is dangerous because it can make your database queries work too well. You might design a query that will be terribly slow on the actual hardware of 30 15K disks.
But keep those things in mind and always do final performance testing on a system that looks just like the real thing and you can do almost all your development work on a notebook.
Any notebook should be able to run any software supported on the OS that its running. You should absolutely have no issues using it for coding, and low impact databases for testing. You wouldn't want to use it to host sites to the world.