MySql——delete

delete t1 
from 
	tjyx.member_card_balance t1,
	(select t2.card_no from tjyx.member_card_balance t2,tjyx.member_card t3 where t2.card_no=t3.CARD_NO and (t3.BALANCE>=50 or t2.balance!=t3.BALANCE) ) a 
where a.card_no=t1.card_no;