Unique code from a database sent by online e-mail form

[sieg]

Hello,

 

I would appreciate very much some advice in the following matter:

 

there's this e-mail form with contact details which should be send by the user. Along with the details, I need to setup there a unique alphanumeric code, from a list on a MySQL database or plain text, which should appear on that form. After the form has been sent, the code will delete itself from the database.

 

Any advice how can I do this?

 

Thank you very much indeed.

 

Sieg.