Re: Best way to do this query?

Marshall wrote:

> I run in to this kind of query every so often. I wonder if
> there's a canonical best way to do it?
>
> Consider the following schema:
>
> Invoices:{invoiceid, customerid, date, amount}
>
> Each invoice has an id, the id of the customer who opened the
> invoice, the date of the creation of the invoice, and the amount.
>
> If I want to know the date of every customer's most recent invoice,
> that's easy:
>
> select customerid, max(date) from Invoices group by customerid
>
> But suppose I also want to know the id and amount of that particular
> invoice?

Just as an aside, I was forced to use MySQL 4 for a small project and had a similar query requirement. For those who haven't had the dubious pleasure of using MySQL 4, it's handling of sub queries is tenuous to non-existent, so the approach suggested by Cimode wasn't an option. Hence I ended up with a slightly different approach as follows:

SELECT A.invoiceid, A.customerid, A.date, A.amount, Max(A.date - B.date)
FROM invoices AS A
INNER JOIN invoices AS B
ON A.customerid = B.customerid
GROUP BY A.customerid

Regards, Jim.

>
>
> Marshall
Received on Wed Jan 17 2007 - 15:16:30 CET