UPDATE语句：将一个表里的字段更新到另一个表的字段里的语句

update table2 b,(select b.area_id as arid,sum(a.user_amount) as bcount

from table1 a,table2 b

where a.user_area=b.area_id

group by arid) c

set b.count=c.bcount

where b.area_id=c.arid;