1.创删数据库；
create database mydb;
复杂一点可以设置字符集和校对规则：create database mydb character set gbk collate gbk_chinese_ci;
drop database mydb;
使用数据库 use mydb；
2. 创删表格
创建create table student(id int not null);
删除 drop table student;
增加主键 alter table student change id id int primary key;
删除主键 alter table student drop primary key;
如果主键时自增长，先要去除 alter table student modify id int not null;
增加外键 alter table student add foreign key employee(b_id) references department(b_id);
删除外键（先查看外键约束（有的没有约束））show create table;
alter table score drop foreign key score_ibfk_1;
3. 备份与还原
在cmd命令中备份， mysqldump -uroot -p mydb> d:/mydb.sql
还原， mysqldump -uroot -p mydb < d:/mydb,sql
4. 增删改查
增 alter table student add address varchar(127) not null after sex; #增加一个字段，在sex字段后添加address字段
insert into student values (11, '李磊', '男',23) #插入一条信息
删 alter table student drop address; #删一个字段
delete from student where age>40; #按where条件删除整条信息
改 alter table student modify id int not null; #修改字段
alter table student change id id b_id int; #可以修改字段名称
update student set id=4 where id=1;
update staff set name='张三', id=5 where name='李四'；
查 select * from student where id =5 and sex='男' and age not between 20 and 30; #按条件查询，where，between...and
select b_name, b_id, count(y_name) from (select department.b_name, staff.* from department, staff where department.b_id=staff.b_id) as temp group by b_id order by count(y_name) desc, b_id asc;