count()函数里面想实现带条件统计，可以使用SUM函

SELECT s.user_id,SUM(case(m.is_success) when 1 then 1 else 0 end),SUM(case when m.read_time IS NULL  then 0 else 1 end),COUNT(*) 
from doc_score s,mail_send_log m where s.user_id in(6,7,8,9) and s.status = 1 and m.doc_id = s.doc_id 
group by s.user_id 
;