GROUP BY eats data, why?

Question

MySQL

Hello!
In general, today I asked a question here about grouping several SELECTs. Select with GROUP BY by date from 3 tables, to be exact. As a result, I received an answer, but found a strange work.
To the point.
If I run this code:

SELECT `date`,
       case when `user` = 'new_sites'  then cnt else 0 end as new_sites,
       case when `user` = 'new_users' then cnt else 0 end as new_users,
       case when `user` = 'new_leads' then cnt else 0 end as new_leads
FROM (
SELECT `date`, COUNT(*) AS cnt, 'new_sites' as user FROM  `l_sites` GROUP BY `date`
union all
SELECT `date`, COUNT(*) AS cnt, 'new_users' as user FROM  `l_users` GROUP BY `date`
union all
SELECT `date`, COUNT(*) AS cnt, 'new_leads' as user FROM  `l_leads` GROUP BY `date`
) as T

The result is this:
The dates are repeated, but in general everything is fine. It remains to add GROUP BY `date` at the end and it's over - I thought.
I write the following code:

SELECT `date`,
       case when `user` = 'new_sites'  then cnt else 0 end as new_sites,
       case when `user` = 'new_users' then cnt else 0 end as new_users,
       case when `user` = 'new_leads' then cnt else 0 end as new_leads
FROM (
SELECT `date`, COUNT(*) AS cnt, 'new_sites' as user FROM  `l_sites` GROUP BY `date`
union all
SELECT `date`, COUNT(*) AS cnt, 'new_users' as user FROM  `l_users` GROUP BY `date`
union all
SELECT `date`, COUNT(*) AS cnt, 'new_leads' as user FROM  `l_leads` GROUP BY `date`
) as T GROUP BY `date`

As a result, we get:

Please note that in the first case there are 3 units in the rightmost column, in the second case there are only two with grouping. GROUP BY eats data for 2016-08-24. By the way, the situation is similar with the column in the center.
What is the problem and how to solve?

Answer 1

Во внешнем запросе тоже должны быть функции COUNT() иначе, как GROUP BY догадается, что нужно сделать с группами.