mysql中的缓存机制是如何实施运行的,写了一个子查询,但是查询的速度特别慢,想知道如何优化,附上sql语句:
select
um.user_code,um.user_name,
(SELECT co.NAME FROM cou co WHERE co.id = c.cou_id) cou_name,
c.name class_name,
(SELECT ui.nick FROM user_inter ui WHERE ui.id = cd.tea_id) tea_name,
npf.price money,
a.*
from attend_class_log a
inner join user_mem um on um.id = a.stu_id
inner join cla c on c.id = a.cla_id
inner join cla_date cd on cd.id = a.cla_date_id
left join ncrm_stu_cour_cons nscc on nscc.att_class_log_id = a.id
left join ncrm_payment_his_fund npf on npf.id = nscc.his_fund_id
where 1 = 1