Hard Drive Cable

I am attempting to install a second hard drive on my wife's Dell Precision Workstation 370 . I ordered the new hard drive from Dell several weeks ago, however I am just now getting around to the installation and I do not have the cable that connects the hard drive to the board. My question is does Dell not ship the cable with the hard drive? And if not, why doesn't the sales person suggest we might need this cable? It's Sunday afternoon, and I'm dead in the water.