I have no previous knowledge in Java. My only programming skills is Oracle SQL (passed 1Z0-051 SQL Fundamentals I).
What's the time effort for passing Oracle Certified Associate, Java SE 7 Programmer 1Z0-803? From zero to exam? Hours?
Hard to say. If you just cram knowledge without understanding, you can pass. This takes a few weeks. And I've seen SCJPs who were not able to code their a$$ out of a for loop.
Doing it right and understanding the mechanisms unde the hood takes longer and needs programming experience. A good read: http://norvig.com/21-days.html