Stopping mulitple repeated entries

zrocker

So i have a couple of forms on my website and when people would submit them and hit refresh it wants to place another entry into the database. Is there a way to prevent that from taking place.

I was just thinking of running a delete call to the database upon bring up the admin page... that says... if name and form info is the same as any other rows to delete all but that one... But not sure how to address it correctly... thank you

coldwerturkey

there are lots of difference ways to address this. If it was me, assuming the table is large and you don't want to run a check for duplicate entries every single time, you could use session's and if someone submits the form twice (as recorded by the session) than run the duplicate check + subsequent delete or warning

bradgrafelman

In addition, if there should never be duplicate data, why haven't you added a UNIQUE key?

EDIT: Also, to add to the above; if you use sessions to track whether a form has already been submitted (search the board or Google - this is another somewhat common topic), then there's no need to do a 'delete' check or anything... just stop the INSERT from ever happening.

As I mentioned above though, if you have a situation where you never want duplicate data, adding a UNIQUE key to your database would be a simple way to solve this. That way, when you perform the INSERT query, you can check if MySQL returns an error code stating that a duplicate has occurred and you can then display an appropriate error message.

EDIT2: Guess I should replace 'MySQL' with 'DBMS' since you didn't explicitly state you were using any specific one. :o

zrocker

SO as for using a unique key... is that only to one specific field... or just all the fields?... Let say i set a unique key... on the coding if there is a duplicate entry... how would the coding look..

i will look up as much as i can concerning the unique key but if you can help me with how the coding would work, that would be cool.. thanks

bradgrafelman

zrocker wrote:
as for using a unique key... is that only to one specific field... or just all the fields?

That depends - it doesn't have to be just one column. For example, let's say you stored the user's first name and surname in two different columns. Obviously, placing a UNIQUE key on either column wouldn't achieve the desired result. Instead, you would create a UNIQUE key on both columns simultaneously; that is, one single UNIQUE key that envelopes two (or more) columns.

zrocker wrote:
on the coding if there is a duplicate entry... how would the coding look..

Well, again, you didn't mention a specific DBMS, so I'll assume MySQL.

What you'd do is execute [man]mysql_query/man and check if it returned FALSE (which it does when MySQL detects an error while executing the query). If it does, you'd check if [man]mysql_errorno/man returns error number 1062, or 'Duplicate data for key ...' (or something like that). Note that I am not sure if the duplicate key error number is 1062 - you may want to look that up and verify it. If you're not even using MySQL, then you'd have to look it up anyway for your specific DBMS.