I suppose no matter how much somebody tells you, regardless of their advice, until you have the unfortunate happenstance yourself you're not going to learn except by experience. I'll share the story anyway... ignore it at your own peril. The advice is simple: save your source code in three places. Yes, three. Why?
A long time ago at a faraway company I had the pleasure of developing a state-of-the-art docketing system for a corporate legal department. I did all of my development off the C drive, and then after making any major change I would pull out my 5 1/4 inch disk labeled "Legal System Backup" and copy the source code over to it.
Well the inevitable happened: I had a hard disk crash. No problem, right? At least I have a backup. But after swapping in a spanking new hard drive -- holy O'Reilly: I can't read the floppy disk. Naturally about a week later a clerk in Legal wanted to add a new feature to the system. I could only shrug. I'm so sorry: we lost the source code.
Make three copies: save one or your disk, one on the network, and one in your off-site email box. Because there's no excuse for losing the source code.
Most modern developers work in an environment with built-in source code control, such as TFS or CVS. Occasionally though I've known companies that view their SQL views and stored Procs as something less than legitimate source code. Perhaps they feel a database backup is adequate coverage for the intellectual property.
Your source code (and SQL stuff) however provides an additional benefit to your employer besides being the cogs and gears that make everything work. Its /history/ is valuable for researching bugs. So make sure you not only keep three versions of everything that is currently running, but also keep all of the prior executed versions as well.