On 09/10/10 8:07 PM, tony@exquisiteimages.com wrote:
> Coming from 25 years of programming applications based on dBASE and FoxPro
> tables, I have a question about how to deal with a programming task.
>
> I have a situation where I receive a file with transactions that have a
> unique key from a vendor. These transactions should only be imported into
> my system once, but the vendor system will occasionally resend a
> transaction by mistake.
>
> The way I am currently handling this with Micorosft ADO and FoxPro files
> is to open a table with an index on the vendor key and seek on the key. If
> there is no match I add it, if there is a match I put it in an exception
> file to be manually checked.
>
> Using PostgreSQL I can't open a table and do seeks against an index. I
> could do a select against the database and see if 0 records are returned,
> but that seems to take more time than doing a seek on an index. Is there a
> more SQL friendly way of handling this task?
>
>
the table should have a UNIQUE constraint on that primary key field.
use a transaction.
go to insert the data.
if you get a constraint violation, roll back the transaction, then
insert it into your exceptions table.