[The uniqueness validator of ActiveRecord][1] has an options to skip validation if the value is nil or blank. Even if I set both parameters to true (the default behaviour) I can create one record with nil and blank before the validation hits. I use the default SQlite3 Database sqlite3-ruby (1.2.5).

Edit for clarification: I get the expected result if I add `validates_presence_of` to the Model. I thought that the default behaviour of `validates_uniqueness_of` would make this redundant.

**Testcase:**

    rails validation_test
    cd validation_test/
    script/generate Model Thing identification:string
    rake db:migrate

Content of app/models/thing.rb:

    class Thing &lt; ActiveRecord::Base
      validates_uniqueness_of :identification
    end

Rails console:

    script/console 
    Loading development environment (Rails 2.3.4)
    &gt;&gt; Thing.create!
    =&gt; #&lt;Thing id: 1, identification: nil, created_at: &quot;2009-09-26 01:49:32&quot;, updated_at: &quot;2009-09-26 01:49:32&quot;&gt;
    &gt;&gt; Thing.create! :identification =&gt; &quot;&quot;
    =&gt; #&lt;Thing id: 2, identification: &quot;&quot;, created_at: &quot;2009-09-26 01:49:42&quot;, updated_at: &quot;2009-09-26 01:49:42&quot;&gt;
    &gt;&gt; Thing.create! :identification =&gt; &quot;&quot;
    ActiveRecord::RecordInvalid: Validation failed: Identification has already been taken
    	from /usr/lib/ruby/gems/1.8/gems/activerecord-2.3.4/lib/active_record/validations.rb:1090:in `save_without_dirty!&#39;
    	from /usr/lib/ruby/gems/1.8/gems/activerecord-2.3.4/lib/active_record/dirty.rb:87:in `save_without_transactions!&#39;
    	from /usr/lib/ruby/gems/1.8/gems/activerecord-2.3.4/lib/active_record/transactions.rb:200:in `save!&#39;
    	from /usr/lib/ruby/gems/1.8/gems/activerecord-2.3.4/lib/active_record/connection_adapters/abstract/database_statements.rb:136:in `transaction&#39;
    	from /usr/lib/ruby/gems/1.8/gems/activerecord-2.3.4/lib/active_record/transactions.rb:182:in `transaction&#39;
    	from /usr/lib/ruby/gems/1.8/gems/activerecord-2.3.4/lib/active_record/transactions.rb:200:in `save!&#39;
    	from /usr/lib/ruby/gems/1.8/gems/activerecord-2.3.4/lib/active_record/transactions.rb:208:in `rollback_active_record_state!&#39;
    	from /usr/lib/ruby/gems/1.8/gems/activerecord-2.3.4/lib/active_record/transactions.rb:200:in `save!&#39;
    	from /usr/lib/ruby/gems/1.8/gems/activerecord-2.3.4/lib/active_record/validations.rb:1059:in `create!&#39;
    	from (irb):3
    &gt;&gt; Thing.count
    =&gt; 2

Why do the first two creations pass?

Thanks

  [1]: http://api.rubyonrails.org/classes/ActiveRecord/Validations/ClassMethods.html#M002167

All Validates Uniqueness-Of Solutions on Gang of Coders

Total of 1 Validates Uniqueness-Of Solutions

validates_uniqueness_of passes on nil or blank (without allow_nil and allow_blank)