How can I make this query faster? I've tried a sub-select and an inner join

How can I make this query faster? I've tried a sub-select and an inner join

This is the first query I was working with. The query took way too long to
process. This will be processing millions of rows in the table.
select date(datetime), count(*) from LOG l1
where ((datetime >= str_to_date('2013-01-01 00:00:00','%Y-%m-%d %H:%i:%s'))
and (datetime < str_to_date('2013-01-30 00:00:00','%Y-%m-%d %H:%i:%s'))
and code_subcode in ('8008118', '8008218', '8008318', '8008418'))
and (
select count(*) from log l2
where l2.session_id = l1.session_id and l2.remote_ip = l1.remote_ip and
code_subcode
in('8008119', '8008219', '8008319', '8008419')
and TIMEDIFF(l2.datetime, l1.datetime) < 1)
group by date(datetime) order by date(datetime);
After some reading I found that joins are supposed to be faster than
nested-selects so I converted it to this...
SELECT date(l1.datetime), count(*) from LOG l1
INNER JOIN LOG l2 ON l2.SESSION_ID=l1.SESSION_ID
where ((l1.datetime >= str_to_date('2013-01-01 00:00:00','%Y-%m-%d
%H:%i:%s'))
and (l1.datetime < str_to_date('2013-01-30 00:00:00','%Y-%m-%d %H:%i:%s'))
and l1.code_subcode in ('8008118', '8008218', '8008318', '8008418')
and l2.code_subcode in('8008119', '8008219', '8008319', '8008419')
and date(l1.datetime) = date(l2.datetime)
and TIMEDIFF(l2.datetime, l1.datetime) < 1)
GROUP BY date(l1.datetime)
ORDER BY DATE(l1.datetime);
Please help, thanks.