There is a nice solution in MySQL.
Add the keyword SQL_CALC_FOUND_ROWS right after the keyword SELECT :
SELECT SQL_CALC_FOUND_ROWS t3.id, a,bunch,of,other,stuff FROM t1, t2, t3
WHERE (associate t1,t2, and t3 with each other)
GROUP BY t3.id
LIMIT 10,20
After that, run another query with the function FOUND_ROWS() :
SELECT FOUND_ROWS();
It should return the number of rows without the LIMIT clause.
Checkout this page for more information : http://dev.mysql.com/doc/refman/5.0/en/information-functions.html#function_found-rows