Re: Pulling an ID list from a DB, then filtering that list againstanother list of ID's

Here is what I have for a layout: thing_id -> it is a hash value (md5()) I have a user session variable that is an array "thing_id's that were viewed". So each time the user click a like to view a thing_id, I note that in a session variable, so when they go back to the home page, all the things they have viewed are not shown, only the ones they have not viewed. Thing_id --------- 1 | hash_id_1 2 | hash_id_2 3 | hash_id_3 4 | hash_id_4 Viewed (Session Var) -------------------- 1 | hash_id_2 2 | hash_id_4 So when the user hits the homepage, they should get a list of 2 hash ID's hash_id_1 and hash_id_3. That is how I want this to work, I just need a slick way to compare and filter the viewed hash_id's from the complete list I am pulling form the DB. Does that help? Thanks, Matt On Thu, 2003-08-14 at 16:35, CPT John W. Holmes wrote: > From: "Matt Babineau" <matt@criticalcode.com> > > Got an interesting problem! I have a list of ID's, basically things > > people have viewed on my website. When I pull the viewable items from my > > database, I need to be able to filter out all the ID's people have > > already viewed, so that they only get a list of things they have not > > viewed. > > > > I can think of a way to do this, but it is a nasty loop situation, that > > would probably not be good and tie up significant CPU time. Anyone have > > any suggestions on ways to filter view items from a fresh list that I am > > pulling from my Database? > > So you have a "thing_id" and a "user_id". How do you mark the user as > having > viewed the "thing"? > > I'm thinking a LEFT JOIN is in order here, but need some more info on your > table structure. > > ---John Holmes... >