In our application we are using web-services and DB, is it possible to integrate Selenium webdriver with web-services (Soap UI)?
Since this is in Java, yes it is possible to interact with SoapUI using the test runner or by importing SoapUI into Java and running it as a background task.
If two different frameworks are integrated, whether this is good?.
I don't think the issue you will have will be the different frameworks. I think the issue will be the fact that SoapUI has a horrible integration into being remotely controlled. It's cumbersome, difficult and overall a pain. I would suggest just adding the web services into your Java project and building a harness for it that way you have absolute control easily over the web services.
My expectation is: Have to validate or compare actual result with webservices or DB.
So where is the need for Selenium here? It sounds like you need to call a webservice, check the data against results in the database and have an assertion checking that they match. No need to use Selenium for that.