http://www.dslreports.com/forum/r20442317 en Tue, 02 Dec 2008 19:53:03 EDT Tue, 02 Dec 2008 19:53:03 EDT http://www.dslreports.com/forum/remark,20466180 Ray : That's what I was thinking. It's slow because that subselect is re-run for every row in the outer query. First, I'd create an index on the comment date if there isn't one already and see if that becomes acceptable.

Secondly, I'd try to make a query of the latest comment for each invoice a one-time deal as part of the FROM clause using a table alias. I'd need to create some test data & play with it for a while to actually give you some specific SQL, but something along the lines of

SELECT i.blah, c.comment
FROM invoices i
JOIN (SELECT most recent comment for each invoice) c
ON (c.invoice_id = i.invoice_id)
--
ON DELETE CASCADE]]> http://www.dslreports.com/forum/remark,20466180 Sun, 11 May 2008 16:46:37 EDT http://www.dslreports.com/forum/remark,20449954 jayco437 : I don't know anything about DB2, but my first thought if I was doing this in Postgres would to analyze the table and check the indexes.

Can you change the select max() to a select.... order by comments.date desc limit 1, and notice any improvement?]]> http://www.dslreports.com/forum/remark,20449954 Thu, 08 May 2008 04:41:39 EDT http://www.dslreports.com/forum/remark,20446787 dropshadow : thank you. your solution does indeed work, however it is slow. any way to speed this up? anyone? i want to avoid a subquery if possible, because that's slowing me down...]]> http://www.dslreports.com/forum/remark,20446787 Wed, 07 May 2008 16:06:47 EDT http://www.dslreports.com/forum/remark,20442361 PetePuma : I'd probably do something like

select i.invoiceNumber, i.invoiceAmount,c.invoiceCommentfrom invoices iinner join comments c on i.invoicenumber = c.invoicenumber and c.date = (select max(comments.date) from comments  where c.invoicenumber = comments.invoicenumber)
I think that would work on DB2, it's been a while.

Disclaimer: done without syntax checking.
]]> http://www.dslreports.com/forum/remark,20442361 Tue, 06 May 2008 20:45:49 EDT http://www.dslreports.com/forum/remark,20442317 dropshadow : sorry, yes, by timestamp...so something like comments.dateCreated or something, i don't have the db in front of me atm...]]> http://www.dslreports.com/forum/remark,20442317 Tue, 06 May 2008 20:36:19 EDT http://www.dslreports.com/forum/remark,20441886 PetePuma : How do you determine what is the most recent invoice comment? Is there a timestamp column? Do you want the one with the highest identity?]]> http://www.dslreports.com/forum/remark,20441886 Tue, 06 May 2008 19:10:43 EDT http://www.dslreports.com/forum/remark,20441608 dropshadow : i have a table with invoices. i have another table with invoice comments. what i want to do is perform a join, but only retrieve the most recent comment for each invoice.

basically, what i would like to do is this:

select invoices.invoiceNumber, invoices.invoiceAmount, TOP 1 comments.invoiceComment, from invoices inner join comments on invoices.invoiceNumber = comments.invoiceNumber.

however, my db does not seem to like this syntax. i am on an IBM DB2. it basically understands standard SQL. is there another way to write this statement? what i do not want retrieved is multiple lines of invoices since there are sometimes many comments per invoice.]]> http://www.dslreports.com/forum/remark,20441608 Tue, 06 May 2008 18:20:30 EDT