sqlserver:
UPDATE a SET a.grade=b.id FROM userinfo a,levelinfo b WHERE a.exp>=b.minvalue AND a.exp<b.maxvalue
mysql:
UPDATE userinfo a,levelinfo b SET a.grade=b.id WHERE a.exp>=b.minvalue AND a.exp<b.maxvalue
转载于:https://www.cnblogs.com/andy_tigger/archive/2011/05/10/2042315.html