display Form after selection in "select"

display Form after selection in "select"

Hello,

I want an address or assistance on the following:
in my page I do a form with a simple select
I would like after validation of this select display (without reloading) another form (more complete) after id sent by the 1st form

small precision: the values of the second form are in a BDD and must be displayed

Thank you for your help