Might I suggest setting your table up so that the choice/vote column is only ever 1 or 0. ("1" = vote for photo 1, "0" = vote for photo 2). This should allow you to build slightly faster queries by not having to search on the vote column (also lets you use BIT, but then you might have to convert() later, I'm not sure how MySQL handles bit->int conversions. At least in the tests I did locally, MS SQL won't do the conversion implictly, but I didn't see any performance drops adding an explicit conversion).

The first stat you already have:

select
	post_id,
	sum(choice) as ones,
	count(ip) - sum(choice) as twos
from
	votes
group by
	post_id

The second stat ("wins") you're looking for:

select
	post_id,
	sum(choice) as one_vote,
	count(ip) - sum(choice) as two_vote,
	case
		when sum(choice) > count(ip) - sum(choice) then 1
		when sum(choice) < count(ip) - sum(choice) then 2
		else -1
	end
from
	votes
group by
	post_id

or in aggregate form:

select
	sum(ones) as one_wins,
	sum(twos) as two_wins,
	sum(ties) as ties
from
(
	select
		post_id,
		case when sum(choice) > count(ip) - sum(choice) then 1 else 0 end as ones,
		case when sum(choice) < count(ip) - sum(choice) then 1 else 0 end as twos,
		case when sum(choice) = count(ip) - sum(choice) then 1 else 0 end as ties

	from
		votes
	group by
		post_id
) a

Alternatively/at the very least, you should modify Patrick's logic to include cases where 1 photo receives all of the votes:

select
	coalesce(ones.post_id,twos.post_id) as post_id,
	isnull(ones.votes,0) as one_vote,
	isnull(twos.votes,0) as two_vote,
	case
		when isnull(ones.votes,0) > isnull(twos.votes,0) then 1
		when isnull(ones.votes,0) < isnull(twos.votes,0) then 2
		else -1
	end
from
	(select post_id, count(*) as votes from votes where choice = 1 group by post_id) as ones
full outer join
	(select post_id, count(*) as votes from votes where choice = 2 group by post_id) as twos
on
	ones.post_id = twos.post_id

1. limit the ability to vote one time per IP/Post, or 2. have a unique index on the votes table (ip_address, post_id)?

Either way, Patrick's solution appears to do the trick on MySQL.

Kevin Hillabolt said on February 22, 2008:

case when ones.vote = twos.vote then 1 else 0 end as tie

1 representing true.

select
post_id,
ones.votes as one_vote,
twos.votes as two_vote,
case when ones.votes > twos.votes then 1 else 2 end as winner

from

(select post_id, count(*) as votes from votes where choice = 1 group by post_id) as ones join
(select post_id, count(*) as votes from votes where choice = 2 group by post_id) as twos on
ones.post_id = twos.post_id

Although, that syntax might not work with MySQL. It works for Postgresql and SQL Server.