# Multiple Trees in a better\_nested\_set Table **URL:** \ **Category:** Ruby\ **Created:** [January 15, 2008, 12:34am UTC](https://www.ruby-forum.com/t/multiple-trees-in-a-better-nested-set-table/126046 "2008-01-15T00:34:11Z")\ **Posts on this page:** 1\ **Page:** 1
**Author:** ![sdsykes](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/f14d63/32.png) [@sdsykes](https://www.ruby-forum.com/u/sdsykes)\ **Post date:** [January 15, 2008, 12:34am UTC](https://www.ruby-forum.com/t/multiple-trees-in-a-better-nested-set-table/126046/1 "2008-01-15T00:34:11Z")
Hi All, I also sent this message out to the better\_nested\_set mailing list so I’ll update this thread if that yields a response. I’m having trouble configuring a table to be able to accommodate multiple trees. I have a feeling that this is a common question but a few creative searches came up empty. I tried using [http://wiki.rubyonrails.org/rails/pages/BetterNestedSet](http://wiki.rubyonrails.org/rails/pages/BetterNestedSet) as a guide and created a tree\_id column in my table and declared acts\_as\_nested\_set, :scope =\> :tree\_id in my model. My rspec tests began failing and reporting the MYSQL error below: \*Mysql::Error: #42000You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near ‘? ? “tree\_id IS NULL” : “tree\_id = #{tree\_id}” AND (parent\_id IS NULL)) ORDER B’ at line 1: SELECT \* FROM studies WHERE (tree\_id.nil? ? “tree\_id IS NULL” : “tree\_id = #{tree\_id}” AND (parent\_id IS NULL)) ORDER BY lft \* Any insight is greatly appreciated. I guess I’m a bit hazy on what :scope is used for and how to use it. I’ve also played around with making multiple trees without :scope in my directive and it most of my method calls ended up looking like I’d expect. (.root? and .root got weird on me) -Thanks! Stephen