On Fri, 20 May 2011 09:48:45 -0500, Jack Christensen <jackc@xxxxxxxxxxxxxxxxx> wrote: > On 5/20/2011 8:41 AM, Seb wrote: >> Hi, >> I'm trying to implementing the checking in and checking out of items >> in a table, whereby an item cannot be checked out if it's not >> checked-in. I've searched for schemas for public libraries where >> this is a key requirement, but haven't managed to hit the right >> keywords to get relevant results. >> Thanks, > Use a loans table with unique partial index to ensure that only one > unreturned loan per item can exist at a time. [...] Thanks, this certainly avoids loaning an item before it's returned, but it doesn't protect against having loans that overlap in time. For example, an item can have a start_time that is between start_time and end_time of a previous loan for that same item. My first thought was to have some CHECK constraint with a query, but this doesn't seem to be supported by postgresql. -- Seb -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
