SIMPLE: ASP.NET QNS!

Hi, I have no problem connecting to my database and stuff. But I have a lot of problems selecting the relevent rows. I did database programming normally using SQL codes, but this is my first time doing it integrating with other programming languages. the question is: How do I select individual rows for a column of values when i don't even know the ID of each rows. I believe there must be some syntax, but I have no idea what they are nor can I find it on the net. For example, in this instance: When I add a new user, if a new user happen to register an account with a userid which already exist, they are normally redirected to an error page, stating that there are no duplications in the primary key. What I want to do is to loop through the database before allowing users to register a new userid. It will checks through the list of userids if it does not match any, it will then allow users to register new members. This way, we will not be redirected to an error page. But how do i do this? Using C#??? The thing is for example: Using this code: ///************* SELECT userid FROM loginTable ///************** What happens, is that it returns the entire column of userid, how do i break them down to rows? Thanks Aaron ## Deliverables I just need you to be able to answer this qns. ## Platform ASP.NET SQL