Hi, I'm a little confused, I'm developing a program, the program consist in two parts, the server and the clients, there are groups, places, messages... stored in the server, and the clients has to connect with it. I've design the use cases diagram, the activity diagrams, and I have design the class diagram too.

The thing is that I want to implement the server in a mysql tables for storing the users, groups, places... users in groups... so I've designed a E-R diagram consisting in 6 tables, but the problem is that I think that my class diagram and my ER diagram looks too similar, I mean, I think I'm not doing things right because I have a class for each table practically, and when I have to extract all the users on my system, do I have to convert all the rows into objects at first and write in the database for each object modified?

The easy choice for me would be to base my whole application only in the database, and making a class to extract and insert data in it, but I have to follow the UML specification and I'm a little confused what to do with the class diagram, because the books I have read say that I have to create a class for each "entity" of my program.

Sorry for my bad English.

Thank you.