This is more of a PHP question, or whichever language the website is being written in. I'll use PHP.

Assuming you already know how to do your database search and get results displayed, it's really quite simple. When you go to display the part name on building the page after the query, add the href tag to it. Each link goes to the same webpage afterwards, so:

$part = get next value from result set

echo "<a href=/"form.html?part=".$part."/">".$part."</a>";

Then from your form.html page, get the value of the part variable that we posted in the link and set that as the default value to the form's text.