What simple web-based relational database system would you recommend?

Hello all,

We have just launched a startup. Now, we are looking for a simple web-based relational database system where we can easily add tables and connect them to one another through foreign keys. For example, we would want to create a suppliers database in which we could perform a query such as "show me

  1. all suppliers

  2. for a certain product type

  3. which is based in a certain region

  4. and offers the product type within a certain price range".

We are a team of five which means the database should be accessible for 5 people through a web interface. We know the basics of database modeling. But unfortunately, none of us is experienced in writing (my)SQL code. Thus, we would wish to find a system that comes with a tool-based development environment. Eventually, our budget is limited and we, therefore, would prefer a cheap system over an expensive one. We would appreciate any ideas from you