looking for webpage with database "tricks"

Is there a tutorial on the web explaining how you can do nice stuff with relational databases? Like how webmonkey tries to explain how messages are sorted with a forum. My real question is: * I have a user table * I have an agenda table with messages Now they want me to make agenda categories and users must be able to get a list only of agenda items of the categories they are interested in AND: the categories must be as flexible as can be. One should be able to _add_ a category. I thought of making an extra category table with rows for every category with it's place in order, _and_ put all chosen categories in one field in the users table like cat1*cat3*catn And when making their personal message I will do some great juggling trick with that string. But probably there is a better way. that's why i asked for tutorials... cheers. Chris -------------------------------------------------------------------- Chris Hayes Droevendaalsestg. 35 6708 PB Wageningen the Netherlands http://www.xs4all.nl/~chayes/