python - Complex compound order_by django query -

i have following 2 models title of movies , tv:

title     - id     - title     - show_name (fk, nullable)  tvshow     - id     - title 

here example data entries:

episode_title - (1, "terminator", null) - (2, "zzz", 1) --> fk tvshow (1, "seinfeld") - (3, "abyss", null) 

here how should sorted:

- abyss (sort episode title if show null) - seinfeld - zzz (sort show title if show not null) - terminator (sort title if show null) 

how django queryset? have now, incorrect --

title.objects.filter('title', 'show__title') 

i think want:

title.objects.select_related().extra(     select={'sort_title':"coalesce(`tv_show`.`title`, `title`.`title`)"},     order_by=['sort_title'] ) 

so adding "virtual" field select clause, coalesce give first non-null value, sort_title tv show's title if there one, or regular title. can sort name give it. select_related() join done in 1 query, not sure table names can take there...