Problem setting default value

[Roofbid]

I have a parts list table where the items in the table are sorted into categories. Each part has a ItemID. When adding a new record to the form I want the ItemID field to fill automatically with the next proceeding ItemID number in category of the item being added. I have a variable list box to set the category record source and a variable list box to show the record for the selected ItemID. I tried to set the default value "itemid" +1 and the dbMax() also.

Thanks
Gary

[gobbligook]

Re: Problem setting default value

This is a very common problem.

In most database engines, to know the value of the auto incremented field before actually creating the row is almost a paradox.

In your case the issue becomes a question of whether you want that item id to be accurate. If you do as you suggest, and before you submit the full record, someone else writes to the database, your itemid that you tried to figure out will be wrong.

IE:
You start entering data for ItemID 10
Someone Submits to that table and as a result the value for their itemID becomes 10.
You submit to the table right after, your item ID is in reality 11.

But if you can live with this improbable but possible scenario, then this is the simplest way.

What you can do is create an entry in the db BEFORE you display the new entry box, or perhaps by using an event like a button click. Insted of doing an insert to the database, you essentially are doing an update. However there are problems with this method also, what if the user cancels before submitting? then you've got a blank row in the db. Also you'll have a gap in your index as well.

You wont' be able to write a value to the auto-increment field (assuming you are using an auto-increment field for an index).

I have thought about this question quite a bit, and in my opinion you need to do two writes to the database to get this right. 1) insert blank 2) give user ability to modify blank, and 3) update blank with the users settings.

So in the application I may have an advanced button that when you click creates the record in the db, and displays all relivant boxes/prompts, and then another click for submit on that record. If the user doesn't submit, in my case the db will clean up blank entries on a schedule (I've a stored procedure that runs and does this). In my case the fact that there were gaps in the index didn't matter.

[Roofbid]

Re: Problem setting default value

Thanks for the info; I'll give it a try.

Gary