标准sql update语句三种方法

DROP TABLE IF EXISTS t_test;
CREATE TABLE t_test (
  bs bigint(20) NOT NULL auto_increment,
  username varchar(20) NOT NULL,
  password varchar(20) default NULL,
  remark varchar(200) default NULL,
  PRIMARY KEY  (bs)
) ENGINE=myisam AUTO_INCREMENT=4 DEFAULT CHARSET=gbk;

INSERT INTO t_test VALUES (1,'lavasoft','123456',NULL);
INSERT INTO t_test VALUES (2,'hello',NULL,NULL);
INSERT INTO t_test VALUES (3,'haha',zz,tt);
 

update t_test t
   set t.password = '***'
 where t.bs = 2;

update t_test t
   set t.password = '*', t.remark = '*'
 where t.bs = 1;

update t_test t
   set t.password = null, t.remark = null
 where t.bs = 3;