Can we switch from software testing (QA) to development?

siddheshnisaldoes software testing needs database testing ?

Yes.

and does tester requires programming knowledge of both java and .net ?

Requires - not necessary. Depends on your project's requirement.
But a knowledge of both is definitely going to shine on your resume.

is it possible to switch from testing to development later?👎

Again a yes. The transition isn't as smooth as you want it to be. But, if you talk to the seniors and have proof to show that you can actual 'develop' (Read 'code') applications, you are good to go.