They are called ER diagrams (entity relationship). You'll have much better success if you google the correct term. There are plenty of tools around. We use a proprietary tool, Aqua Data Studio. But looking over the list that shammat posted, this one looks good.
I use Toad Data Modeler for 10 years or so.
That times it was known as: CaseStudio. After bought by another company name has been changed. Unfortunately the prise has been rised about 5 times too
IMO it is best tool for designing databases. Faster than all other I know (comparing to UML tools is useless) and very convenient while using.
It supports a log of DB engines, including single release versions. Provide lot of features like reverse engineering. But mainly it is ERD modeling tool. So don't expect IDE for writing SQL.