Question

I need help from you, this is my sql query:

select count(SID) 
from Test 
where Date = '2012-12-10' 
group by SID

this is my result:

|2|
|3|
|4|
|3|

and now I have to count the results from first query!

Expected result: 4 

Answer 1

You can wrap your query in another SELECT:

select count(*)
from
(
  select count(SID) tot  -- add alias
  from Test 
  where Date = '2012-12-10' 
  group by SID
) src;  -- add alias

See SQL Fiddle with Demo

In order for it to work, the count(SID) need a column alias and you have to provide an alias to the subquery itself.