select count(1) from l left join j on j.userID=l.userid 
 where l.appID=1000 and l.loginTime>='2018-01-01' and l.loginTime<'2018-02-01'

select l.* into #tmp
 from l  where l.appID=1000  and l.loginTime>='2018-01-01' and l.loginTime<'2018-02-01'   

 select count(1) from #tmp l left join j on j.userID=l.userid