Prevent multiple inserts of same data?

Anon

I have the user input info into a form which is then submitted to another page which inserts the info to the database and displays the results. How can I prevent multiple inserts of the same data if say, the user hits the refresh button? I'm assuming it would try to perform all the database operations when it refreshed.

tomhath

You can either do a SELECT on every column before the INSERT, or go ahead with the INSERT and then check if there are two identical rows (except for an auto-increment column of course) and delete based on the ID you just inserted. If your dbms supports it you should wrap the queries in a BEGIN TRANSACTION - COMMIT block.

bretticus

I usually just query the table with the form data before inserting data like tomhath suggested. Another really "cheap" way though is to insert the data, then query LAST_INSERT_ID() (mySQL here ;-) then set a header("Location: script.php?id=$lastinsertid"); where script is simply a page that looks up the results of any table record with the id just created (or inserted). If the user hits the refresh button, they just get the results again, no duplicates ;-)

Anon

Are you saying that the entire record should be unique, sounds like a composite Primary Key.

If it is defined as the Primary Key in the database then an error will be produced by the database when a duplicate is entered.

Anon

So how would that look? I'm not sure how to use the Location. Would it be:
<?php

do all my database stuff

$query_eval = "select LAST_INSERT_ID() from some_db";
$lastinsertid = mysql_query($query_eval)

header("Location: script.php?id=$lastinsertid");