2017-02-25
现有count_table、alarm_table两张表，分别如下：
需求：依据cust_id分组查询alarm_table表中各个cust_id今天的告警次数count(*)，用count(*)更新count_table表对应cust_id的alarm_count数据
SQL语句如下：
update
count_table c inner join
(select count(*) cout,cust_id from alarm_table
where
to_days(alarm_date) = to_days(now())
group by cust_id) z
on c.cust_id = z.cust_id
set
c.alarm_count=z.cout,c.date=current_date
where
c.cust_id = z.cust_id;
结果如下：
