# Dedupping Has\_many through, :unique=\>true **URL:** \ **Category:** Rails\ **Created:** [December 20, 2006, 12:13am UTC](https://www.ruby-forum.com/t/dedupping-has-many-through-unique-true/79867 "2006-12-20T00:13:29Z")\ **Posts on this page:** 3\ **Page:** 1
**Author:** ![3nd3r](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/3/c4cdca/32.png) [@3nd3r](https://www.ruby-forum.com/u/3nd3r)\ **Post date:** [December 20, 2006, 12:13am UTC](https://www.ruby-forum.com/t/dedupping-has-many-through-unique-true/79867/1 "2006-12-20T00:13:29Z")
Hi, In the Agile book, it is told that by putting a :unique =\> true will dedup the row with ActiveRecord. But it’s not working out for me. Do I need edge rails for this? I simply want to dedup any join model associations, for instance: category\_id | inventory\_id 384 1 first entry 384 2 this would be ok. 384 1 this would not be ok Any help is appreciated. Thanks ---
**Author:** ![3nd3r](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/3/c4cdca/32.png) [@3nd3r](https://www.ruby-forum.com/u/3nd3r)\ **Post date:** [December 20, 2006, 5:59pm UTC](https://www.ruby-forum.com/t/dedupping-has-many-through-unique-true/79867/2 "2006-12-20T17:59:37Z")
On 12/19/06, Dominic S. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > Hi, In the Agile book, it is told that by putting a :unique =\> true will > dedup the row with ActiveRecord. > > But it’s not working out for me. Do I need edge rails for this? Use :uniq =\> true (note the spelling which matches Ruby’s Array#uniq method) on 1.2 or later. jeremy ---
**Author:** ![3nd3r](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/3/c4cdca/32.png) [@3nd3r](https://www.ruby-forum.com/u/3nd3r)\ **Post date:** [December 21, 2006, 12:02am UTC](https://www.ruby-forum.com/t/dedupping-has-many-through-unique-true/79867/3 "2006-12-21T00:02:51Z")
On 12/20/06, Dominic S. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > 384 1 first entry > 384 2 this would be ok. > 384 1 this would not be ok > > Any help is appreciated. Thanks I’m not 100% on :unique =\> true but you should be able to put validation into your join model to prevent these kinds of issues. eg validates\_uniqueness\_of :category\_id, :scope =\> :inventory\_id might do the trick.