I have a question from an exercise that I am struggling with or to get grips with. I have to write all of them in relational notation in terms of drives etc etc. Sorry I cannot post my solutions to the other questions to show you exactly what I am trying to achieve. Here is the question, I have been presented with drives: PERSON <-> CARS. I have been asked to list the people who drive BMW but not VW. I have also been asked to list the other cars (ie not including VW) driven by the people who drive a VW.
For list the people who drive BMW but not VW if I put a range restriction to show those that drive BMW I could also have a list of people that drive BMW and VW and that would not work and I cannot have a range restriction and an additional range restriction. I am trying to avoid having in my list people that drive both BMW and VW.
For the list the other cars (ie not including VW) driven by the people who drive a VW, I am not sure how to go about solving this besides have a range restriction inside another range restriction.