Is it possible to order posts by two meta values?

Question

Hopefully this is a reasonably straightforward question!

Is it possible to order posts, on the front-end of my WP install, by two meta values?

I have a meta key called genus and another called species. I'd like to sort firstly by genus (ASC), then species (ASC).

Thanks in advance,

Answer 1

AFAIK, you can't do it using a meta query. Check this example, does what you want.

Answer 2

The simplest solution I can think of is to join the posts meta table with posts table twice. Modifying codex example a bit you can use this:

$querystr = "
SELECT wposts.* 
FROM $wpdb->posts wposts, $wpdb->postmeta wpostmeta1, $wpdb->postmeta wpostmeta2
WHERE wposts.ID = wpostmeta1.post_id
AND wposts.ID = wpostmeta2.post_id
AND wpostmeta1.meta_key = 'genus'
AND wpostmeta2.meta_key = 'species'
AND wposts.post_type = 'post'
ORDER BY wpostmeta1.meta_value ASC,
         wpostmeta2.meta_value ASC
";