This is a very basic question but I hope it is not a problem that I ask.

I am developing an interface that will update a database from another database. The two databases are for applications we did not develop.

For each input record, it is not known whether a record needs to be created in the other database. I am interested in knowing if there is much difference in whether we:

(1) first do a query to determine if the record exists, then do either an insert or an update

(2) do an update first and if the record does not exist then do an insert

One advantage to doing the query first is that we can determine when the data has actually changed. Are there any other significant advantages or disadvantages?

For what it is worth, the output database is an Access database; the input database is a SQL Server database but could be another database format such as dbase.

Is this a one-shot migration of the data from source to destination or will it be ongoing?

This will be a regular process, run aproximately daily. It will probably be scheduled to run overnight without interaction, but the user will run it whenever needed.

im in a similar situation and trying to do the same process..but mine is db2 udb os/390 to db2 udb windows..it's like populating the win2k server's database.

but im doing it using a java program..u can see my post in 'data manipulation' forum.