# Use join table in paginate **URL:** \ **Category:** Rails\ **Created:** [May 22, 2006, 9:07pm UTC](https://www.ruby-forum.com/t/use-join-table-in-paginate/61293 "2006-05-22T21:07:30Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![koenwarner](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/k/46a35a/32.png) [@koenwarner](https://www.ruby-forum.com/u/koenwarner)\ **Post date:** [May 22, 2006, 9:07pm UTC](https://www.ruby-forum.com/t/use-join-table-in-paginate/61293/1 "2006-05-22T21:07:30Z")
How come I allways immediately run into difficult stuff when I’m trying some new programming language? Am I blind for the simplicity of Ruby/Rail, which a see must be there? Anyway, don’t try and answer this rhetoric question. I have got another one for you, seemingly difficult. I’m struggling with a n:m relationship (in a database, that is) and its join table. Here are my objects: class Painting has\_and\_belongs\_to\_many :themes which maps to db entity painting id class Theme has\_and\_belongs\_to\_many :paintings which maps to db entity theme id And of course the join table paintings\_themes painting\_id theme\_id So, paintings have one or more themes, and a theme can belong to more paintings. In my ExpositionController, which shows the paintings, I have: @painting\_pages, @paintings = paginate :paintings, :per\_page =\> 10 But now I want only to show paintings with a certain theme (still paginated of course). So I have to put a :condition in the paginating code. I’ve tried something like: @painting\_pages, @paintings = paginate :paintings, :per\_page =\> 10, :conditions =\> [‘displayable=? AND themes[0].name=?’, true, ‘flowers’] which shows only displayable paintings with theme=flowers, but the themes[0].name part doesn’t compile. I’m stuck. My mind simple goes blank on this theme (pardon the confusing last term). Anyone who can help me out? Thanks. ---
**Author:** ![koenwarner](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/k/46a35a/32.png) [@koenwarner](https://www.ruby-forum.com/u/koenwarner)\ **Post date:** [May 22, 2006, 9:43pm UTC](https://www.ruby-forum.com/t/use-join-table-in-paginate/61293/2 "2006-05-22T21:43:41Z")
The :conditions portion of you statement should be thought of as generic sql. So in this case you want to filter on a value in the themes table. I’m not positive if you need to use the :include clause to include the “themes” table in the query. Since your query is using multiple tables, you may need to prefix each table column with the table name. @painting\_pages, @paintings = paginate :paintings, :per\_page =\> 10, :conditions =\> [‘displayable=? AND themes.name=?’, true, ‘flowers’], :include =\> :theme ---
**Author:** ![koenwarner](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/k/46a35a/32.png) [@koenwarner](https://www.ruby-forum.com/u/koenwarner)\ **Post date:** [May 22, 2006, 9:49pm UTC](https://www.ruby-forum.com/t/use-join-table-in-paginate/61293/3 "2006-05-22T21:49:49Z")
On May 22, 2006, at 12:07 PM, Koen Warner wrote: > How come I allways immediately run into difficult stuff when I’m > trying > some new programming language? That’s easy! It’s because when you’re learning new things, everything is difficult. 🙂 > something like: > > @painting\_pages, @paintings = paginate :paintings, :per\_page =\> 10, > :conditions =\> [‘displayable=? AND themes[0].name=?’, true, > ‘flowers’] Look up :include. You can create join queries with it, then you’ll be able to specify themes.name=? as you have in mind. I’m curious as to how you arrived at the themes[0] syntax. :conditions are SQL, and that syntax is ruby… – – Tom M. ---
**Author:** ![koenwarner](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/k/46a35a/32.png) [@koenwarner](https://www.ruby-forum.com/u/koenwarner)\ **Post date:** [May 23, 2006, 12:30am UTC](https://www.ruby-forum.com/t/use-join-table-in-paginate/61293/4 "2006-05-23T00:30:23Z")
Steven H. wrote: > The :conditions portion of you statement should be thought of as generic > sql. So in this case you want to filter on a value in the themes > table. I’m not positive if you need to use the :include > clause to include the “themes” table in the query. Since your query is > using multiple tables, you may need to prefix each table column with the > table name. > > @painting\_pages, @paintings = paginate :paintings, :per\_page =\> 10, > :conditions =\> [‘displayable=? AND themes.name=?’, true, ‘flowers’], > :include =\> :theme Great Steven. It works! The only thing I had to adjust in your proposal was :include =\> :themes in stead of :include =\> :theme I’m still not sure as to what exactly happens, but I’ll have a look at the logfile to see the executed SQL. That will clear things up. Thanks a lot. ---
**Author:** ![koenwarner](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/k/46a35a/32.png) [@koenwarner](https://www.ruby-forum.com/u/koenwarner)\ **Post date:** [May 23, 2006, 12:34am UTC](https://www.ruby-forum.com/t/use-join-table-in-paginate/61293/5 "2006-05-23T00:34:54Z")
Tom M. wrote: > That’s easy! > > It’s because when you’re learning new things, everything is > difficult. 🙂 > Guess your right. > Look up :include. > I’ll certainly look into ‘include’, it seems usefull as Steven pointed > out to. > I’m curious as to how you arrived at the themes[0] syntax. :conditions > are SQL, and that syntax is ruby… > That’s why my sample code didn’t work 🙂 > You can use the syntax in something like > @@my\_log.debug("==\>ExpositionController: a painting > #{painting.themes[0].name}") > because the painting object has an array of themes, and here we’ll grab > the first one. But in SQL of course this won’t work. Thanks for the helpful reply.