How can I design database? how can I create tables, relations based on case studies and diagrams? is there a software for designing DB's, I know UML is used for designing classes and functions but what about DB?
UML in general is used just to see the whole structure, but not that useful when it comes to DB implementation. I have some experience with Rational Rose but I found it a bit hard to design DBs. What I do is : get a sheet of paper and input all the data from diagrams / case studies. Then see what relationships are visible and start the implementation process. Test the working model and you'll see what you've missed during the "design" cause there's always something. Hope this can help.
Ottodo - there are companies that specialise in "patterns" for various industries. You buy one and then build the application - knowing that the underlying database is well thought out and complete. I haven't seen any small projects using them but I'm sure they're out there. Search for database+patterns
db designer is a free quite basic Entity-Attribute-Relationship modelling tool aimed mainly at MySQL db design. So if you want to build a relational MySQL database it's a great choice. Cons are its limited functionality and lack of support for other databases.