样式一:
update xcs_user_credit_score a1,xcs_user_credit_score a2
set a1.user_currday_score=a1.user_currday_increment_score+a2.user_currday_score
where a1.pt_day='2017-09-20' and a2.pt_day='2017-09-19'
and a1.uid=a2.uid;
样式二:
update xcs_user_credit_score a1
inner join xcs_user_credit_score a2
on a1.uid=a2.uid
set a1.user_currday_score=a1.user_currday_increment_score+a2.user_currday_score
where a1.pt_day='2017-09-20' and a2.pt_day='2017-09-19'
;