How to create a database?

Hi,

I would like to create a database in which I can insert rows and columns and edit specific rows and columns of the database as my matlab code is being run. I've never worked with databases before. Please help. I would like to use the database to store usernames and passwords.Anytime that I open and run my matlab code, I will continuously edit or add new usernames and passwords to the database.

It would be superb if you could provide me with a code that does the above.

An example is better than two lectures.

Thanks.