# Rails Query within Query **URL:** \ **Category:** Rails\ **Created:** [March 13, 2009, 1:24am UTC](https://www.ruby-forum.com/t/rails-query-within-query/162714 "2009-03-13T01:24:29Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![aviir](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/ecb155/32.png) [@aviir](https://www.ruby-forum.com/u/aviir)\ **Post date:** [March 13, 2009, 1:24am UTC](https://www.ruby-forum.com/t/rails-query-within-query/162714/1 "2009-03-13T01:24:29Z")
Hello, I am looking for a better way to do the following (my code examples are crappy pseudocode): I have two associated models, Book and Chapter, where book has\_many chapters. I want to first select several books, for example, books\_by\_dr\_seuss = Book.find(:all, :conditions =\> {:author =\> “Seuss” }) Then, I want to select all the “Chapter 3”'s from this result, i.e. Chapter 3 of Cat in the Hat, Chapter 3 of Fox in Socks, etc. I want to do something like: chapter\_threes = Chapter.find(:all, :include=\>[:book], :conditions =\> {chapter.book in books\_by\_dr\_seuss } ) How would I do this without resorting to something like “select \* from chapters where chapter.book\_id=1 or chapter.book\_id=2, etc”? Thanks for your help. A ---
**Author:** ![aviir](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/ecb155/32.png) [@aviir](https://www.ruby-forum.com/u/aviir)\ **Post date:** [March 13, 2009, 1:32am UTC](https://www.ruby-forum.com/t/rails-query-within-query/162714/2 "2009-03-13T01:32:18Z")
Wouldn’t it be something like the following: suess\_chapter\_three = Chapter.find(:all, :include=\>:book, :conditions =\> [‘books.auther like “suess” and chapters.chapter = 3’]) Simon ---
**Author:** ![aviir](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/ecb155/32.png) [@aviir](https://www.ruby-forum.com/u/aviir)\ **Post date:** [March 13, 2009, 1:54am UTC](https://www.ruby-forum.com/t/rails-query-within-query/162714/3 "2009-03-13T01:54:30Z")
I think something like the following: book\_ids = ids of selected books (as gleened from the controller) chapter\_threes = Chapter.find(:all, :include =\> :book, :conditions =\> [‘book.id in ? and chapter.chapter\_number = 3’, book\_ids]) obviously not tested, but once you fix any syntax errors it should work. Simon ---
**Author:** ![aviir](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/ecb155/32.png) [@aviir](https://www.ruby-forum.com/u/aviir)\ **Post date:** [March 13, 2009, 1:46am UTC](https://www.ruby-forum.com/t/rails-query-within-query/162714/4 "2009-03-13T01:46:14Z")
Simon M. wrote: > Wouldn’t it be something like the following: > > suess\_chapter\_three = Chapter.find(:all, :include=\>:book, :conditions =\> > [‘books.auther like “suess” and chapters.chapter = 3’]) > > Simon Thanks for the response Simon – I think my example didn’t fully capture what I am trying to do 🙂 I want to select from a collection or list of items. I can’t use ‘books.author like’ because there is no criteria that ties them all together. A better example would be: User is presented with a list of checkboxes (let’s say, book names) in a form. He checks several of these checkboxes. The form gets submitted and returns all of the chapters 3 from the selected books. For example say the user selects: Fox in Sock by Dr Seuss War and Peace by Leo Tolstoy The Godfather by Mario Puzo The form passes the ids of these selections (let’s say, [1000, 1001, 1002]) to the controller, which then calls a query on these selected plates: selected\_books = params[:selected\_books] Chapter.find(:all, :include=\>:book, :conditions =\> ‘chapter.book\_id = book.id and book.id in books and chapters.chapter=3’ ) Is there a way to do that statement? “in books” is obviously not a valid command… Thanks! A ---
**Author:** ![aviir](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/ecb155/32.png) [@aviir](https://www.ruby-forum.com/u/aviir)\ **Post date:** [March 18, 2009, 6:02pm UTC](https://www.ruby-forum.com/t/rails-query-within-query/162714/5 "2009-03-18T18:02:06Z")
Thank you for the reply Simon. What you said worked for me, although I did it in a rather inelegant way – I’m not sure about the correct syntax of my solution, but it works. It requires creating a string with the ids in parens… book\_ids = “(100, 101, 102)” chapters= Chapter.find(:all, :include =\> :books, :conditions =\> [“books.id in #{book\_ids} and chapter=‘2’”] Any suggestions for clearer code welcome, but thank you for your help! ---
**Author:** ![aviir](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/ecb155/32.png) [@aviir](https://www.ruby-forum.com/u/aviir)\ **Post date:** [March 18, 2009, 6:37pm UTC](https://www.ruby-forum.com/t/rails-query-within-query/162714/6 "2009-03-18T18:37:17Z")
On Mar 18, 5:02 pm, Avi Ir [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > Thank you for the reply Simon. What you said worked for me, although I > did it in a rather inelegant way – I’m not sure about the correct > syntax of my solution, but it works. It requires creating a string with > the ids in parens… > > book\_ids = “(100, 101, 102)” > chapters= Chapter.find(:all, :include =\> :books, :conditions =\> > [“books.id in #{book\_ids} and chapter=‘2’”] first off that can be done nicer: book\_ids = [1,2,3] chapters= Chapter.find(:all, :include =\> :books, :conditions =\> [“books.id in (?) and chapter=‘2’”, book\_ids] or even chapters= Chapter.find(:all, :include =\> :books, :conditions =\> { ‘books.id’ =\> book\_ids, ‘chapter’ =\> 2}) You don’t even need to get an array of book\_ids - an array of activerecord objects will do fine too. And last of all: Chapter.find :all, :joins =\> :books, :conditions =\> {‘books.author’ =\> ‘Seuss’, ‘chapter’ =\> 2} Fred ---
**Author:** ![aviir](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/ecb155/32.png) [@aviir](https://www.ruby-forum.com/u/aviir)\ **Post date:** [March 18, 2009, 6:59pm UTC](https://www.ruby-forum.com/t/rails-query-within-query/162714/7 "2009-03-18T18:59:24Z")
Hi Fred, Thanks for your response – Your second example is exactly what I needed. The final example, though – why do you use :joins instead of :include?