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drop database if exists school;
create database school default charset utf8;
-- 切换到数据库school
use school;
-- 创建学生表
drop table if exists tb_student;

create table tb_student
(
stuid int not null comment '学号',
stuname varchar(20) not null comment '姓名',
stusex bit default 1 comment '性别',
stubirth date comment '生日', 
primary key (stuid)
);
alter table tb_student add column stuaddr varchar(255);
alter table tb_student change column stuaddr stuaddr varchar(511);
-- alter table tb_student drop column stuaddr;
insert into tb_student values(1003, '张三丰',1,'1982-2-2','湖北十堰');
insert into tb_student values(1004, '张二丰',1,'1982-2-2','湖北十堰');
insert into tb_student values(1005, '张一丰',1,'1982-2-2','湖北十堰');
insert into tb_student (stuid,stuname,stusex) values (1006,'素素',0);
insert into tb_student (stuid,stuname,stusex) 
    values
        (1007,'杨逍',1),
        (1008,'谢逊',1),
        (1009,'杨不悔',0);
        
-- 截断表
-- truncate table tb_student-- 

-- 删除学生delete
delete from tb_student where stuid=1003;

--这是因为 MySql 运行在 safe-updates模式下，该模式会导致非主键条件下无法执行update或者delete命令，执行如下命令：
set sql_safe_updates=0;
delete from tb_student where stusex=0;