[Koha] SQL for items with a lot of holds

[Chris Cormack]

On 29 June 2011 10:24, Cindy Weber <cweber at scls.lib.wi.us> wrote:
> I'm trying to write a report that will list items with the number of
> holds/items over a certain number and then list the number of holds
> placed per library.  Since the holds to items ratio is different
> depending on the format of the item (book, DVD, CD, etc.) I'm thinking
> I've got to have one report for each item type.
>
> My initial attempt:
> SELECT biblio.biblionumber, reserves.branchcode AS 'Library',
> biblio.title AS 'Title', COUNT(items.biblionumber) AS 'Copies',
> COUNT(reserves.biblionumber) AS 'Holds'
> FROM biblio
> LEFT JOIN items ON (items.biblionumber = biblio.biblionumber)
> LEFT JOIN reserves ON (reserves.biblionumber = items.biblionumber)
> LEFT JOIN biblioitems ON (biblioitems.biblionumber = biblio.biblionumber)
> WHERE items.ccode = 'BK%'
> GROUP BY biblio.biblionumber HAVING
> (COUNT(reserves.biblionumber)/COUNT(items.biblionumber)) > 15
>
>
> When trying to troubleshoot why this didn't return any results, I
> discovered that
> SELECT biblio.title, COUNT(items.biblionumber), COUNT(reserves.biblionumber)
> FROM biblio
> JOIN items ON (items.biblionumber = biblio.biblionumber)
> JOIN reserves ON (reserves.biblionumber = biblio.biblionumber)
>
> returned really large numbers and the items and holds numbers wer all
> equal.  For a specific bibionumber, it gave me 520 for both the count of
> items and the count of reserves.  There are 8 holds and 65 items for
> that biblionumber.  So it's multiplying the two counts together and
> returning that as the result.  Changing the JOIN types didn't help any.
> Can anyone please tell me what I'm doing wrong and how to fix this?
>
Hi Cindy

We can try, but since you aren't running an official release of Koha,
we can only guess at your database structure.  What you probably want
to do, is group the results by biblionumber. You are trying to find
out the number of reserves, and the number of items for each
biblionumber right?

Chris