how to populate the combo box with the database data

hi everyone,

I created a table in the database using .install file.now i want to load some 10 entries(3 fields) of an employee.I want to populate the combo box of the form with 10 employee ids.If anyone enters the form for the first time, I have to autogenerate password and sent to their mail.How to acheive this.Its very urgent.Give me some some suggestions and clues.

Thanks,
Vijay