SELECT `date`,
case when `user` = 'tot_user' then cnt else null end as tot_user,
case when `user` = 'tot_user2' then cnt else null end as tot_user2,
case when `user` = 'tot_user3' then cnt else null end as tot_user3
FROM (
SELECT `date`, COUNT(*) AS cnt, 'tot_user' as user FROM `l_sites` GROUP BY `date`
union all
SELECT `date`, COUNT(*) AS cnt, 'tot_user2' as user FROM `l_users` GROUP BY `date`
union all
SELECT `date`, COUNT(*) AS cnt, 'tot_user3' as user FROM `l_leads` GROUP BY `date`
) as T