Which percent of my new users became paying users in a particular period of time?

select  concat(string( 100*( payer/register) ),'%')   as registered_to_paying from 
 (select  1 as dummy, count(distinct uid) as register
from cooladata 
where date_range(doc.date_range) 
and doc.slicers
and event_name='newPlayer') a
join 
(select  1 as dummy, count(*) as payer
from accounts 
where  is_paying=1  ) b 
on a.dummy=b.dummy