MySql 笔记

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;