用root账号管理其他用户

#创建用户

mysql> create user 'jasonhz'@'localhost' identified by '123456';

#给用户授权

mysql> grant all privileges on myschool.* to 'jasonhz'@'localhost';

#刷新授权

mysql> flush privileges;

#更改用户密码

mysql> set password for 'jasonhz'@'localhost' = password('111222');

#删除用户

mysql> drop user 'jasonhz'@'localhost';

SQL语句(Structured Query Language 结构化查询语言)

DDL (Data Definition Language 数据定义语言) 如：CREATE DROP ALTER

DML( Data Manipulation Language 数据操纵语言) 如： INSERT UPDATE DELETE

DQL(Data Query Language 数据查询语言) 如：SELECT

DCL(Data Control Language 数据库控制语言) 如：GRANT COMMIT ROLLBACK

DDL (Data Definition Language 数据库定义语言)

#创建数据库

mysql> create database if not exists hzdb;

#使用数据库

mysql> use hzdb;

#查看所有可访问的数据库

#除了hzdb是自己创建的，mysql系统中有四个默认的库 information_schema 、 mysql、performance_schema、sys

mysql> show databases;

+--------------------+

| Database |

+--------------------+

| information_schema |

| hzdb |

| mysql |

| performance_schema |

| sys |

+--------------------+

#删除数据库

mysql> drop database hzdb;

#查看数据库支持的引擎

mysql> show engines;

#查看数据库默认的引擎

mysql> show variables like '%storage_engine%';

#查看当前数据库的编码

mysql> show variables like '%char%';

#创建表

mysql> create table person(

-> `id` int(4) primary key auto_increment comment '编号',

-> `name` varchar(50) not null default '无名氏' comment '姓名',

-> `address` varchar(100) comment '地址'

-> )engine=innodb default charset=utf8 comment='人员信息';

#查看所有表

mysql> show tables;

#查看表的结构

mysql> desc person;

+---------+--------------+------+-----+-----------+----------------+

| Field | Type | Null | Key | Default | Extra |

+---------+--------------+------+-----+-----------+----------------+

| id | int(4) | NO | PRI | NULL | auto_increment |

| name | varchar(50) | NO | | 无名氏 | |

| address | varchar(100) | YES | | NULL | |

+---------+--------------+------+-----+-----------+----------------+

#修改表名

mysql> alter table person rename student;

#添加字段

mysql> alter table student add `phone` varchar(13) comment '电话';

#修改字段属性，不能修改表名

mysql> alter table student modify `phone` int(11);

#修改字段，同时修改表名

mysql> alter table student change `phone` `tel` varchar(50) not null;

#删除字段

mysql> alter table student drop `tel`;

#删除表，删除数据要慎重

mysql> drop table student;

DML( Data Manipulation Language 数据操纵语言)

#添加数据

mysql> insert into student (`id`,`name`) values ('1','张三');

mysql> insert into student (`id`,`name`) values ('4','张三'),('6','李四'),('8','王五');

#修改数据

mysql> update student set `name`='李靖' where id=1;

#删除数据

mysql> delete from student where id=1;

#删除所有数据，两种方法

mysql> delete from student;

mysql> truncate table student;

DQL(Data Query Language 数据查询语言)

(有需要sql脚本做练习的请联系我)

#基本查询：

#查询student表中全部信息

mysql> select * from student;

#通过student表，查询`studentNo`,`studentName`,`phone`,`address`,`birthday`字段的信息

mysql> select studentNo, studentName, phone, address, birthday from student;

#通过student表，查询`studentNo`,`studentName`,`phone`,`address`,`birthday`字段的信息，使用as重命名列名显示

mysql> select studentNo as 学号,studentName as 姓名,phone as 电话,address as 地址,birthday as 生日 from student;

#查询email值为null的空行

mysql> select * from student where email is null;

#把成绩都降低10%后加5分，再查询及格成绩，并按照成绩从高到低排序(order by)

mysql> select studentNo as 学号, (studentResult*0.9+5) as 成绩 from result where (studentResult*0.9+5)>60 order by studentResult desc;

#查询所有年级编号为1的学员信息，按学号升序排序，从第5条记录开始显示4条数据(limit)

mysql> select * from student where gradeId=1 order by studentNo asc limit 4,4;

#编写SQL语句，查看年龄比“李斯文”小的学生，要求显示这些学生的信息

mysql> select studentName, birthday from student where birthday>(select birthday from student where studentName='李斯文');

#查询参加最近一次Logic Java考试成绩的学生的最高分和最低分

mysql> select max(studentResult) 最高分,min(studentResult) 最低分 from result where examDate=(select max(examDate) from result where subjectNo=(select subjectNo from subject where subjectName='LogicJava'));

#查询“LogicJava”课程考试成绩为60分的学生名单(采用 IN 子查询 )

mysql> select studentNo, studentName from student where studentNo in(select studentNo from result where subjectNo=(select subjectNo from subject where subjectName='LogicJava'));

#查询参加“LogicJava”课程最近一次考试的在读学生名单

mysql> select studentNo, studentName from student where studentNo in( select studentNo from result where examDate=(select max(examDate) from result where subjectNo=(select subjectNo from subject where subjectName='LogicJava')));

#查询未参加“LogicJava”课程最近一次考试的在读学生名单(not in)

mysql> select studentNo, studentName from student where studentNo not in( select studentNo from result where examDate=(select max(examDate) from result where subjectNo=(select subjectNo from subject where subjectName='LogicJava')));

#查询大一学期开设的课程

mysql> select subjectName from subject where gradeId=(select gradeId from grade where gradeName='大一');

#查询未参加“HTML”课程最近一次考试的在读学生名单

mysql> select studentNo, studentName from student where studentNo not in( select studentNo from result where examDate=(select max(examDate) from result where subjectNo=(select subjectNo from subject where subjectName='HTML')));

#高级查询：

#查看没有参加考试的学生

mysql> select studentName from student where studentNo in (select studentNo from result where studentResult is null);

#检查“LogicJava”课程最近一次考试成绩,如果有80分以上的成绩，显示分数排在前5名的学员学号和分数

mysql> select studentNo, studentResult from result where exists (select studentResult from result where examDate=(select max(examDate) from result where subjectNo=(select subjectNo from subject where subjectName='LogicJava')) and studentResult > 80) order by studentResult desc limit 5;

#检查“Logic Java”课程最近一次考试成绩,如果全部通过考试(60分及格)计算的该次考试平均分减5分

mysql> select avg(studentResult)-5 平均分 from result where exists(select studentResult from result where examDate=(select max(examDate) from result where subjectNo=(select subjectNo from subject where subjectName='LogicJava')) and studentResult > 60);

#如果有大一的学生，就查询参加大一学科考试的学员学号、科目编号、考试成绩，考试时间

mysql> select studentNo 学号, subjectNo 科目编号, studentResult 成绩, examDate 考试时间 from result where exists (select studentNo from student where gradeId=(select gradeID from grade where gradeName='大一'));

#查询每门课程的平均分，并且按照分数由高到低的顺序排列显示(分组查询)

mysql> select subjectNo 课程编号,avg(studentResult) 平均分 from result group by subjectNo order by avg(studentResult) desc;

#分别统计每个年级男、女生人数

mysql> select count(*) 人数, sex 性别 from student group by sex;

#如何获得课程平均分及格的课程编号？(分组筛选语句)

mysql> select subjectNo 课程编号,avg(studentResult) 平均分 from result group by subjectNo having avg(studentResult)>80;

#查询出学生姓名，学生的年级，学生的课程，考试分数，考试时间字段的学生信息(多表查询)

mysql> select studentName 姓名, gradeName 年级, subjectName 课程,studentResult 成绩,examDate 考试时间 from student inner join grade on student.gradeId = grade.gradeID inner join subject on student.gradeId=subject.gradeID inner join result on student.studentNo=result.studentNo;

DCL(Data Control Language 数据库控制语言)

#事务处理，只支持innodb和bdb类型的数据表

#关闭自动提交，同时开启一个事务

mysql> set autocommit=0;

mysql> update acc set `money`=`money`-500 where `name`='Tom';

mysql> update acc set `money`=`money`+500 where `name`='Jerry';

#提交，将数据写入到数据库保存

mysql> commit;

#回到事务处理前的状态，如果已经提交成功，则回滚无效

mysql> rollback;

#打开自动提交

mysql> set autocommit=1;

数据库备份与恢复

#使用mysqldump备份

$ > mysqldump -u root -p myschool > /users/jason/myschool.sql;

#使用source恢复

mysql> use testdatabase;

mysql> source /user/jason/myschool.sql;