How do I manage multiple entries on a single table in a database

[Jennish]

Here's the basic thing
I created a form tools which let users to create their own forms and maintain the data online which is stored in a Mysql database table.
The serial number is primary key.
The problem started when I logged into the fform with three different accounts from three systems at a time.
Thesserial number was same in all the three system and when it saves the data as you can imagine, it will store only one system's input and rest of them won't be able to work.


So how can I resolve this.
I mean if multiple user are working on same form no. how do it resolve while inserting to dB.

 

[Tango]

Make a column 'locked' with timestamp, if the timestamp is say <1h old show a message like 'the project is currently being worked on do you want to continue' you could add many things like locked & last Ip and check if another user is using the form and show 'another user is currently using this form' when a form is submitted clear the timestamp, or you can use php sessions if you read up on the functions.