hibernate CommandAcceptanceException: Error executing DDL

schema.spi.CommandAcceptanceException: Error executing DDL "alter table idm_role_users add constraint FKbbb0hf3h6de22q346hty2916d foreign key (users_id) references idm_user (id)"

某一个表中已经存在数据；此时不能拥修改表约束；

CREATE TABLE IF NOT EXISTS `student`(
`id` INT(11) AUTO_INCREMENT,
`name` VARCHAR(32),
`age` int(11),
`t_id` int(11),
PRIMARY KEY ( `id` )
)ENGINE=InnoDB DEFAULT CHARSET=utf8;

CREATE TABLE IF NOT EXISTS `teacher`(
`id` INT(11) AUTO_INCREMENT,
`name` VARCHAR(32),
`age` int(11),
`t_id` int(11),
PRIMARY KEY ( `id` )
)ENGINE=InnoDB DEFAULT CHARSET=utf8;

insert into teacher values(1,'zs',19,1);

-- ------------------

alter table student add constraint fff_k1 foreign key (t_id) references teacher (id);