I would recommend going on the Oakland Police site: http://www.oaklandpolice.com
I think you can see the breakdown of crime in more detail there. Violent crime is crime where bodily injury occurs: battery (injury without weapons), assault, sexual crimes, murder obviously.
People often make the distinction between violent and non-violent crime. Having your home broken into and nobody hurt is a lot different than a "violent" crime where someone was attacked in the home during the burglary. Sometime violent crimes are committed during a robbery or burglary, and sometimes they stand on their own. Violent criminals are more dangerous in general, for obvious reasons.
I was on the Neighborhood Watch Steering committee in Oakland for a few years and am involved still in neighborhood watch. I strongly recommend checking out the local NCPC (Neighborhood Crime Prevention Council) near you or where you are considering moving/buying property. You can access the list through the City website: http://www.oaklandnet.com
or call the City Council person in the district where a property is..and find out about neighborhood watch, block clubs etc. that meet. The Police attend the NCPC meetings and you can get a ton of info there! Good luck