Checking if an e-mail had already been added to a database
<p>I am editing an ASP form that is basically a newsletter subscription form. The issue is that I have no way of triggering an event alerting me if a user has already registered.</p>

<p>I want to find a way to make the form check if that user's e-mail address exists within my database. If so, then just say, "You have already registered. Did you not receive a thank you email? Click here to receive the email again."</p>

<p>As it stands, the user can register and they automatically get the Thank you form, but are not necessarily told whether they've already registered or not.</p>

<p>EDIT: Sorry for not mentioning this earlier, but this database is managed using Microsoft's SQL Server. Yes, I am storing values using this method. Please let me know if I can include any more details -- I'm not very familiar with DBs.</p>
