mysql产生随机数并连接字符串

concat('a','b','c');//连接字符串

rand();//产生随机数

floor();//取整数

UPDATE user set reg_ip= concat(floor(RAND() * 250),'.',floor(RAND() * 250),'.',floor(RAND() * 250),'.',floor(RAND() * 250)) where username='xxx'