-- 1
select card.*
from user,card
where isLock='0' ORDER BY openDate ;
-- 2
select userId,count(cardNo)
from card
GROUP BY userId;
-- 3
select *
from card
ORDER BY money desc LIMIT 3;
-- 4
select *
from card
where openDate<'2019-04-01' ORDER BY money desc LIMIT 1;
-- 5
select userId,sum(money)
from card
GROUP BY userId