Rails 4 - 按属性的顺序排序

Question

Using Rails 4. Psql DB.

I have a model Article with an attribute amazon_title . I am having trouble understanding how I can order my articles so articles with the amazon_title present are first, and ones without are second.

I've tried ordering them like this with no success:

Article.all.order(amazon_title: :desc)

The above orders it alphabetically, showing blank first, present second, and nil third.

I feel like this is very simple, but for some reason I cannot find the answer. Thanks!

Answer 1

For PostgreSQL (the order will be true , false , nil ):

Article.order('amazon_title DESC NULLS LAST')

Another option (database agnostic):

Article.order('(CASE WHEN amazon_title THEN 1 WHEN amazon_title IS NULL THEN 2 ELSE 3 END) ASC')

Answer 2

In PostgreSQL you can pass NULLS FIRST OR NULLS LAST depending on your requirement. That's why I asked you about your DB.

Article.order('amazon_title DESC NULLS FIRST')

the above will list the NULLS first and

Article.order('amazon_title DESC NULLS LAST')

and this one will list the NULL records last.

Hope that helps!