They happen on a case by case basis, literally. The legislature may pass a law at noon on the penalty for armed robbery, and then the next statute entered into the books is about property rights. The situation in court is the same. A judge may issue an opinion in a murder case right after ruling on an election dispute. Anyone who uses the Internet should understand the situation very well.
Nothing is really organized on the web either.
The answer is the same in both cases, You just have to know where to look and keep looking some more. Bookmarks and search engines help on the Internet. In the law library, legal encyclopedias and digests collect cases that share similar facts or laws. Eventually, you collect enough information to recommend a course of action to a client. Then some new law or judgment changes things again.