Database query error when joining

I was editing the profile fields, and now when someone trys to join, it gives a database query error..

How can I fix this..

I figured this out. I had to view the error report. There was an unrecognized fild, I deleted it in PHP Myadmin, and now it works.

It is also best to post the entire database error message so we can see what is happening.  However, checking the logs is always one of the first things you want to do.