一天学会MYSQL数据库_笔记
2024-05-08 07:46:46
视频是b站的：
一天学会MYSQL数据库
说是说一天，但我看了三四天，有点基础可能看的更加快。我直接从notepad中把自己做的笔记粘过来了~
第一章 mysql建表约束
--mysql 学习笔记----关系型数据库--一、如何使用终端操作数据库--1.如何登录数据库服务器？
widows:mysql -uroot -p123456--2.如何查询数据库服务器中所有的数据库？
mysql>show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| mysql |
| performance_schema |
| sys |
+--------------------+
4 rows in set (0.01 sec)--3.如何选中一个数据库进行操作？
mysql> select * from admin;--4.如何退出数据库？
mysql> exit;
Bye--5.如何在数据库服务器中创建我们的数据库？
mysql> create database test;
Query OK, 1 row affected (0.00 sec)mysql> use test;
Database changed--6.如何查看某个数据库中所有的数据表？
mysql> show tables;
Empty set (0.00 sec)--7.如何创建一个数据表？
CREATE TABLE pet(name VARCHAR(20),owner VARCHAR(20),species VARCHAR(20),sex CHAR(1),birth DATE,death DATE);mysql> CREATE TABLE pet(-> name VARCHAR(20),-> owner VARCHAR(20),-> species VARCHAR(20),-> sex CHAR(1),-> birth DATE,-> death DATE);
Query OK, 0 rows affected (0.05 sec)--8.查看数据是否创建成功
mysql> show tables;
+----------------+
| Tables_in_test |
+----------------+
| pet |
+----------------+
1 row in set (0.00 sec)--9.查看创建好的数据表的结构
mysql> describe pet;
+---------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+---------+-------------+------+-----+---------+-------+
| name | varchar(20) | YES | | NULL | |
| owner | varchar(20) | YES | | NULL | |
| species | varchar(20) | YES | | NULL | |
| sex | char(1) | YES | | NULL | |
| birth | date | YES | | NULL | |
| death | date | YES | | NULL | |
+---------+-------------+------+-----+---------+-------+
6 rows in set (0.01 sec)--10.如何查看数据表中的记录？
mysql> select * from pet;
Empty set (0.00 sec)--11.如何往数据表中添加数据记录？
mysql> INSERT INTO pet-> VALUES ('Puffball','Jane','hamster','f','1999-03-31',NULL);
Query OK, 1 row affected (0.00 sec)--12.再一次查询？
mysql> select * from pet;
+----------+-------+---------+------+------------+-------+
| name | owner | species | sex | birth | death |
+----------+-------+---------+------+------------+-------+
| Puffball | Jane | hamster | f | 1999-03-31 | NULL |
+----------+-------+---------+------+------------+-------+
1 row in set (0.00 sec)INSERT INTO pet
VALUES ('旺财','TK','狗','公','2009-01-31',NULL);mysql> INSERT INTO pet-> VALUES ('旺财','TK','狗','公','2009-02-31',NULL);
ERROR 1292 (22007): Incorrect date value: '2009-02-31' for column 'birth' at row 1
mysql> INSERT INTO pet-> VALUES ('旺财','TK','狗','公','2009-01-31',NULL);
Query OK, 1 row affected (0.00 sec)mysql> select * from pet;
+----------+-------+---------+------+------------+-------+
| name | owner | species | sex | birth | death |
+----------+-------+---------+------+------------+-------+
| Puffball | Jane | hamster | f | 1999-03-31 | NULL |
| 旺财 | TK | 狗 | 公 | 2009-01-31 | NULL |
+----------+-------+---------+------+------------+-------+
2 rows in set (0.00 sec)--13.mysql 常用数据类型有哪些？
--MySQL支持多种类型，大致可以分为三类：数值、日期/时间和字符串(字符)类型。
--数值
create table testType(number TINYINT);
INSERT INTO testType VALUES(128);mysql> INSERT INTO testType VALUES(128);
ERROR 1264 (22003): Out of range value for column 'number' at row 1
类型 大小 范围（有符号） 范围（无符号） 用途
TINYINT 1 byte (-128，127) (0，255) 小整数值
SMALLINT 2 bytes (-32 768，32 767) (0，65 535) 大整数值
MEDIUMINT 3 bytes (-8 388 608，8 388 607) (0，16 777 215) 大整数值
INT或INTEGER 4 bytes (-2 147 483 648，2 147 483 647) (0，4 294 967 295) 大整数值
BIGINT 8 bytes (-9,223,372,036,854,775,808，9 223 372 036 854 775 807) (0，18 446 744 073 709 551 615) 极大整数值
FLOAT 4 bytes (-3.402 823 466 E+38，-1.175 494 351 E-38)，0，(1.175 494 351 E-38，3.402 823 466 351 E+38) 0，(1.175 494 351 E-38，3.402 823 466 E+38) 单精度
浮点数值
DOUBLE 8 bytes (-1.797 693 134 862 315 7 E+308，-2.225 073 858 507 201 4 E-308)，0，(2.225 073 858 507 201 4 E-308，1.797 693 134 862 315 7 E+308) 0，(2.225 073 858 507 201 4 E-308，1.797 693 134 862 315 7 E+308) 双精度
浮点数值
DECIMAL 对DECIMAL(M,D) ，如果M>D，为M+2否则为D+2 依赖于M和D的值 依赖于M和D的值 小数值--日期/时间
类型 大小
( bytes) 范围 格式 用途
DATE 3 1000-01-01/9999-12-31 YYYY-MM-DD 日期值
TIME 3 '-838:59:59'/'838:59:59' HH:MM:SS 时间值或持续时间
YEAR 1 1901/2155 YYYY 年份值
DATETIME 8 1000-01-01 00:00:00/9999-12-31 23:59:59 YYYY-MM-DD HH:MM:SS 混合日期和时间值
TIMESTAMP 4
1970-01-01 00:00:00/2038结束时间是第 2147483647 秒，北京时间 2038-1-19 11:14:07，格林尼治时间 2038年1月19日 凌晨 03:14:07YYYYMMDD HHMMSS 混合日期和时间值，时间戳--字符串(字符)
类型 大小 用途
CHAR 0-255 bytes 定长字符串
VARCHAR 0-65535 bytes 变长字符串
TINYBLOB 0-255 bytes 不超过 255 个字符的二进制字符串
TINYTEXT 0-255 bytes 短文本字符串
BLOB 0-65 535 bytes 二进制形式的长文本数据
TEXT 0-65 535 bytes 长文本数据
MEDIUMBLOB 0-16 777 215 bytes 二进制形式的中等长度文本数据
MEDIUMTEXT 0-16 777 215 bytes 中等长度文本数据
LONGBLOB 0-4 294 967 295 bytes 二进制形式的极大文本数据
LONGTEXT 0-4 294 967 295 bytes 极大文本数据--数据类型如何选择？
日期 选择按照格式
数值和字符串按照大小！INSERT INTO PET VALUES('Slim','Benny','snake','m','1998-09-28',NULL);
INSERT INTO PET VALUES('Fat','Benny','snake','m','1998-09-28',"2299-12-26");--14.如何删除数据？DELETE from pet where name='Fat';mysql> DELETE from pet where name='Fat';
Query OK, 1 row affected (0.01 sec)--15.如何修改数据？
update pet set name='旺旺旺财' where owner='TK';mysql> update pet set name='旺旺旺财' where owner='TK';
Query OK, 1 row affected (0.01 sec)
Rows matched: 1 Changed: 1 Warnings: 0--总结一下：数据库常见操作？
--增加
INSERT
--删除
DELETE
--修改
UPDATE
--查询
select--16.mysql建表约束.sql--a.主键约束它能够唯一确定一张表中的一条记录，也就是我们通过给某个字段添加约束，就可以使得该字段
不重复且不为空create table user(id int primary key,name varchar(20));insert into user value(1,'张三');mysql> insert into user value(1,'张三');
Query OK, 1 row affected (0.01 sec)mysql> insert into user value(1,'张三');
ERROR 1062 (23000): Duplicate entry '1' for key 'PRIMARY'insert into user value(2,'张三');
mysql> select * from user;
+----+--------+
| id | name |
+----+--------+
| 1 | 张三 |
| 2 | 张三 |
+----+--------+
2 rows in set (0.00 sec)mysql> insert into user value(null,'张三');
ERROR 1048 (23000): Column 'id' cannot be null--b.联合主键
--只要联合的主键加起来不重复就可以
create table user2(id int,name varchar(20),password varchar(20),primary key(id,name)
);insert into user2 values(1,'张三','123');
insert into user2 values(2,'张三','123');
insert into user2 values(1,'李四','123');insert into user2 values(null,'李四','123');
mysql> insert into user2 values(null,'李四','123');
ERROR 1048 (23000): Column 'id' cannot be null--c.自增约束
create table user3(id int primary key auto_increment,name varchar(20)
);insert into user3(name) values('张三');mysql> insert into user3(name) values('张三');
Query OK, 1 row affected (0.00 sec)mysql> select * from user3;
+----+--------+
| id | name |
+----+--------+
| 1 | 张三 |
+----+--------+
1 row in set (0.00 sec)mysql> insert into user3(name) values('张三');
Query OK, 1 row affected (0.00 sec)mysql> select * from user3;
+----+--------+
| id | name |
+----+--------+
| 1 | 张三 |
| 2 | 张三 |
+----+--------+
2 rows in set (0.00 sec)-- 如果说我们创建表的时候，忘记创建主键约束了，怎么办？
create table user4(id int,name varchar(20)
);mysql> desc user4-> ;
+-------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+-------------+------+-----+---------+-------+
| id | int(11) | YES | | NULL | |
| name | varchar(20) | YES | | NULL | |
+-------+-------------+------+-----+---------+-------+
2 rows in set (0.00 sec)--修改表的结构，添加主键
alter table user4 add primary key(id);mysql> desc user4;
+-------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+-------------+------+-----+---------+-------+
| id | int(11) | NO | PRI | NULL | |
| name | varchar(20) | YES | | NULL | |
+-------+-------------+------+-----+---------+-------+
2 rows in set (0.00 sec)--如何删除？
alter table user4 drop primary key;mysql> alter table user4 drop primary key;
Query OK, 0 rows affected (0.05 sec)
Records: 0 Duplicates: 0 Warnings: 0mysql> desc user4;
+-------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+-------------+------+-----+---------+-------+
| id | int(11) | NO | | NULL | |
| name | varchar(20) | YES | | NULL | |
+-------+-------------+------+-----+---------+-------+
2 rows in set (0.00 sec)--使用modify修改字段，添加约束
alter table user4 modify id int primary key;mysql> alter table user4 modify id int primary key;
Query OK, 0 rows affected (0.05 sec)
Records: 0 Duplicates: 0 Warnings: 0mysql> desc user4;
+-------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+-------------+------+-----+---------+-------+
| id | int(11) | NO | PRI | NULL | |
| name | varchar(20) | YES | | NULL | |
+-------+-------------+------+-----+---------+-------+
2 rows in set (0.00 sec)--d.唯一约束
--约束修饰的字符不可重复
create table user5(id int,name varchar(20)
);alter table user5 add unique(name);mysql> alter table user5 add unique(name);
Query OK, 0 rows affected (0.02 sec)
Records: 0 Duplicates: 0 Warnings: 0mysql> desc user5;
+-------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+-------------+------+-----+---------+-------+
| id | int(11) | YES | | NULL | |
| name | varchar(20) | YES | UNI | NULL | |
+-------+-------------+------+-----+---------+-------+
2 rows in set (0.00 sec)insert into user5 values(1,'zhangsan');mysql> insert into user5 values(1,'zhangsan');
Query OK, 1 row affected (0.01 sec)mysql> insert into user5 values(1,'zhangsan');
ERROR 1062 (23000): Duplicate entry 'zhangsan' for key 'name'--name=lisi
mysql> insert into user5 values(1,'lisi');
Query OK, 1 row affected (0.01 sec)create table user6(id int,name varchar(20),unique(name)
);create table user7(id int,name varchar(20) unique
);create table user8(id int,name varchar(20),unique(id,name)
);-- unique(id,name)表示两个键在一起不重复就行
mysql> create table user8(-> id int,-> name varchar(20),-> unique(id,name)-> );
Query OK, 0 rows affected (0.03 sec)mysql> desc user8;
+-------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+-------------+------+-----+---------+-------+
| id | int(11) | YES | MUL | NULL | |
| name | varchar(20) | YES | | NULL | |
+-------+-------------+------+-----+---------+-------+
2 rows in set (0.00 sec)insert into user8 values(1,'zhangsan');
insert into user8 values(2,'zhangsan');
insert into user8 values(1,'lisi');
mysql> select * from user8;
+------+----------+
| id | name |
+------+----------+
| 1 | lisi |
| 1 | zhangsan |
| 2 | zhangsan |
+------+----------+
3 rows in set (0.00 sec)-- 如何删除唯一约束？
alter table user7 drop index name;mysql> alter table user7 drop index name;
Query OK, 0 rows affected (0.02 sec)
Records: 0 Duplicates: 0 Warnings: 0mysql> desc user7;
+-------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+-------------+------+-----+---------+-------+
| id | int(11) | YES | | NULL | |
| name | varchar(20) | YES | | NULL | |
+-------+-------------+------+-----+---------+-------+
2 rows in set (0.00 sec)-- modify 添加alter table user7 modify name varchar(20) unique;mysql> alter table user7 modify name varchar(20) unique;
Query OK, 0 rows affected (0.02 sec)
Records: 0 Duplicates: 0 Warnings: 0mysql> desc user7;
+-------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+-------------+------+-----+---------+-------+
| id | int(11) | YES | | NULL | |
| name | varchar(20) | YES | UNI | NULL | |
+-------+-------------+------+-----+---------+-------+
2 rows in set (0.00 sec)--总结：
--1、建表的时候就添加约束
--2、可以使用 alter... add...
--3、alter... modify...
--4、删除alter... drop...--非空约束
--修饰的字符不能为空 NULLcreate table user9(id int,name varchar(20) NOT NULL
);mysql> create table user9(-> id int,-> name varchar(20) NOT NULL-> );
Query OK, 0 rows affected (0.03 sec)mysql> desc user9;
+-------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+-------------+------+-----+---------+-------+
| id | int(11) | YES | | NULL | |
| name | varchar(20) | NO | | NULL | |
+-------+-------------+------+-----+---------+-------+
2 rows in set (0.00 sec)insert into user9 values(1);mysql> insert into user8 values(1);
ERROR 1136 (21S01): Column count doesn't match value count at row 1insert into user9 values(1,'zhangsan');mysql> insert into user9 values(1,'zhangsan');
Query OK, 1 row affected (0.01 sec)mysql> select * from user9;
+------+----------+
| id | name |
+------+----------+
| 1 | zhangsan |
+------+----------+
1 row in set (0.00 sec)insert into user9(name) values('lisi');mysql> insert into user9(name) values('lisi');
Query OK, 1 row affected (0.00 sec)mysql> select * from user9;
+------+----------+
| id | name |
+------+----------+
| 1 | zhangsan |
| NULL | lisi |
+------+----------+
2 rows in set (0.00 sec)--e.默认约束
--就是当我们插入字段的时候，如果没有传值，就会使用默认值create table user10(id int,name varchar(20),age int default 10
);mysql> desc user10;
+-------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+-------------+------+-----+---------+-------+
| id | int(11) | YES | | NULL | |
| name | varchar(20) | YES | | NULL | |
| age | int(11) | YES | | 10 | |
+-------+-------------+------+-----+---------+-------+
3 rows in set (0.00 sec)insert into user10 (id,name) values(1,'zhangsan');mysql> insert into user10 (id,name) values(1,'zhangsan');
Query OK, 1 row affected (0.01 sec)mysql> select * from user10;
+------+----------+------+
| id | name | age |
+------+----------+------+
| 1 | zhangsan | 10 |
+------+----------+------+
1 row in set (0.00 sec)insert into user10 values(1,'zhangsan',18);mysql> insert into user10 values(1,'zhangsan',18);
Query OK, 1 row affected (0.01 sec)mysql> select * from user10;
+------+----------+------+
| id | name | age |
+------+----------+------+
| 1 | zhangsan | 10 |
| 1 | zhangsan | 18 |
+------+----------+------+
2 rows in set (0.00 sec)--f.外键约束
--涉及到两个表：父表、子表
--主表、副表。--班级
create table classes(id int primary key,name varchar(20)
);-- 学生表
create table students(id int primary key,name varchar(20),class_id int,foreign key(class_id) references classes(id)
);insert into students values(1001,'张三',1);
insert into students values(1002,'张三',2);
insert into students values(1003,'张三',3);
insert into students values(1004,'张三',4);insert into students values(1005,'李四',5);mysql> insert into students values(1005,'李四',5);
ERROR 1452 (23000): Cannot add or update a child row: a foreign key constraint fails (`test`.`students`, CONSTRAINT `students_ibfk_1` FOREIGN KEY (`class_id`) REFERENCES `classes` (`id`))insert into classes values(1,'一班');
insert into classes values(2,'二班');
insert into classes values(3,'三班');
insert into classes values(4,'四班');mysql> select * from classes;
+----+--------+
| id | name |
+----+--------+
| 1 | 一班 |
| 2 | 二班 |
| 3 | 三班 |
| 4 | 四班 |
+----+--------+
4 rows in set (0.01 sec)-- 1 主表(父表) classes 中没有的数据值 ，在副表（子表）中，是不可以使用的
-- 2 主表中的记录被副表引用，是不可以被删除的。delete from classes where id=4;
mysql> delete from classes where id=4;
ERROR 1451 (23000): Cannot delete or update a parent row: a foreign key constraint fails (`test`.`students`, CONSTRAINT `students_ibfk_1` FOREIGN KEY (`class_id`) REFERENCES `classes` (`id`))--二、如何使用可视化工具操作数据库？--三、如何在编程语言中操作数据库？
第二章 数据库的三大设计范式
-- 数据库的三大范式.sql--1.第一范式
-- 1NF-- 数据表中的所有字段都是不可分割的原子值create table student2(id int primary key,name varchar(20),address varchar(30)
);insert into student2 values(1,'zhangsan','成都郫都区');
insert into student2 values(2,'wangwu','成都金牛');
insert into student2 values(3,'lisi','成都武侯区');mysql> select * from student2;
+----+----------+-----------------+
| id | name | address |
+----+----------+-----------------+
| 1 | zhangsan | 成都郫都区 |
| 2 | wangwu | 成都金牛 |
| 3 | lisi | 成都武侯区 |
+----+----------+-----------------+
3 rows in set (0.00 sec)-- 字段值还可以继续拆分的，就不满足第一范式
create table student3(id int primary key,name varchar(20),country varchar(30),province varchar(30),city varchar(30),details varchar(30)
);insert into student3 values(1,'zhangsan','中国','四川省','成都市','郫都区1号');
insert into student3 values(2,'wangwu','中国','四川省','成都市','金牛区2号');
insert into student3 values(3,'lisi','中国','四川省','成都市','武侯区3号');mysql> select * from student3;
+----+----------+---------+-----------+-----------+---------------+
| id | name | country | province | city | details |
+----+----------+---------+-----------+-----------+---------------+
| 1 | zhangsan | 中国 | 四川省 | 成都市 | 郫都区1号 |
| 2 | wangwu | 中国 | 四川省 | 成都市 | 金牛区2号 |
| 3 | lisi | 中国 | 四川省 | 成都市 | 武侯区3号 |
+----+----------+---------+-----------+-----------+---------------+
3 rows in set (0.00 sec)-- 范式，设计的越详细，对于某些实际操作可能更好，但是不一定都是好处-- 2.第二范式
-- 必须满足第一范式的前提下， 第二范式要求，除主键外的每一列都必须完全依赖于主键
-- 如果出现不完全依赖 ，只可能发生在联合主键的情况下--订单表create table myOrder(product_id int,customer_id int,product_name varchar(20),customer_name varchar(20),primary key(product_id,customer_id)
);-- 问题？
-- 除主键外的其他列，只依赖于与主键的部分字段
-- 拆表create table myOrder(order_id int primary key,product_id int,customer_id int
);create table product(id int primary key,product_name varchar(20)
);create table customer(id int primary key,customer_name varchar(20)
);-- 分成三个表，就满足了第二范式的设计！！-- 3.第三范式
-- 3NF
-- 必须先满足第二范式，除开主键列的其他列之间不能有传递依赖关系。create table myOrder(order_id int primary key,product_id int,customer_id int
);create table customer(int primary key,name varchar(20),phone varchar(15)
);第三章 mysql查询练习
-- mysql 查询练习学生表
Student
学号
姓名
性别
出生年月日
所在班级
create table student(sno varchar(20) primary key,sname varchar(20) not null,ssex varchar(20) not null,sbirthday datetime,class varchar(20)
); 教师表
Teacher
教师编号
教师名字
教师性别
出生年月日
职称
所在部门
create table teacher(tno varchar(20) primary key,tname varchar(20) not null,tsex varchar(20) not null,sbirthday datetime,prof varchar(20) not null,depart varchar(20) not null
); 课程表
Course
课程号
课程名称
教师编号
create table course(cno varchar(20) primary key,cname varchar(20) not null,tno varchar(20) not null,foreign key(tno) references teacher(tno)
); 成绩表
Score
学号
课程号
教师编号
create table score(sno varchar(20) not null,cno varchar(20) not null,degree decimal,foreign key(sno) references student(sno),foreign key(cno) references course(cno),primary key(sno,cno)
);-- 往数据表添加数据
#添加学生信息
insert into student values('101','曾华','男','1977-09-01','95033');
insert into student values('102','匡明','男','1972-09-01','95031');
insert into student values('103','王丽','女','1974-09-01','95033');
insert into student values('104','李军','男','1974-09-01','95033');
insert into student values('105','王芳','女','1976-09-01','95031');
insert into student values('106','陆君','男','1978-09-01','95031');
insert into student values('107','王尼玛','男','1975-09-01','95033');
insert into student values('108','张全蛋','男','1976-09-01','95031');
insert into student values('109','赵铁柱','男','1974-09-01','95031');#添加教师表
insert into teacher values('804','李成','男','1958-12-02','副教授','计算机系');
insert into teacher values('856','张勋','男','1969-9-18','讲师','电子工程系');
insert into teacher values('825','王萍','女','1972-6-13','助教','计算机系');
insert into teacher values('831','刘冰','女','1986-10-10','助教','电子工程系');#添加课程表
insert into course values('3-105','计算机导论','825');
insert into course values('3-245','操作系统','804');
insert into course values('6-166','数字电路','856');
insert into course values('9-888','高等数学','831');#添加成绩表
insert into score values('103','3-245','86');
insert into score values('105','3-245','75');
insert into score values('109','3-245','68');
insert into score values('103','3-105','92');
insert into score values('105','3-105','88');
insert into score values('109','3-105','76');
insert into score values('103','6-166','85');
insert into score values('105','6-166','79');
insert into score values('109','6-166','81');
#insert into score values('103','3-105','64');
#insert into score values('105','3-105','91');
#insert into score values('109','3-105','78');--查询练习
-- 1、查询student表的所有记录
mysql> select * from student;
+-----+-----------+------+---------------------+-------+
| sno | sname | ssex | sbirthday | class |
+-----+-----------+------+---------------------+-------+
| 101 | 曾华 | 男 | 1977-09-01 00:00:00 | 95033 |
| 102 | 匡明 | 男 | 1972-09-01 00:00:00 | 95031 |
| 103 | 王丽 | 女 | 1974-09-01 00:00:00 | 95033 |
| 104 | 李军 | 男 | 1974-09-01 00:00:00 | 95033 |
| 105 | 王芳 | 女 | 1976-09-01 00:00:00 | 95031 |
| 106 | 陆君 | 男 | 1978-09-01 00:00:00 | 95031 |
| 107 | 王尼玛 | 男 | 1975-09-01 00:00:00 | 95033 |
| 108 | 张全蛋 | 男 | 1976-09-01 00:00:00 | 95031 |
| 109 | 赵铁柱 | 男 | 1974-09-01 00:00:00 | 95031 |
+-----+-----------+------+---------------------+-------+
9 rows in set (0.00 sec)--2、查询student表中所有记录的sname、ssex和class列
mysql> select sname,ssex,class from student;
+-----------+------+-------+
| sname | ssex | class |
+-----------+------+-------+
| 曾华 | 男 | 95033 |
| 匡明 | 男 | 95031 |
| 王丽 | 女 | 95033 |
| 李军 | 男 | 95033 |
| 王芳 | 女 | 95031 |
| 陆君 | 男 | 95031 |
| 王尼玛 | 男 | 95033 |
| 张全蛋 | 男 | 95031 |
| 赵铁柱 | 男 | 95031 |
+-----------+------+-------+
9 rows in set (0.00 sec)--3、查询教师所在的单位即不重复的depart列
mysql> select distinct depart from teacher;
+-----------------+
| depart |
+-----------------+
| 计算机系 |
| 电子工程系 |
+-----------------+
2 rows in set (0.00 sec)--4、查询score表中成绩在60到80之间的所有记录
-- 查询区间 between ... and ...
mysql> select * from score where degree between 60 and 80;
+-----+-------+--------+
| sno | cno | degree |
+-----+-------+--------+
| 105 | 3-245 | 75 |
| 105 | 6-166 | 79 |
| 109 | 3-105 | 76 |
| 109 | 3-245 | 68 |
+-----+-------+--------+
4 rows in set (0.00 sec)--直接使用运算符比较
mysql> select * from score where degree > 60 and degree < 80;
+-----+-------+--------+
| sno | cno | degree |
+-----+-------+--------+
| 105 | 3-245 | 75 |
| 105 | 6-166 | 79 |
| 109 | 3-105 | 76 |
| 109 | 3-245 | 68 |
+-----+-------+--------+
4 rows in set (0.00 sec)--5、查询score表中成绩为85，86或88的记录
--表示 或者关系的查询 in
mysql> select * from score where degree in(85,86,88);
+-----+-------+--------+
| sno | cno | degree |
+-----+-------+--------+
| 103 | 3-245 | 86 |
| 103 | 6-166 | 85 |
| 105 | 3-105 | 88 |
+-----+-------+--------+
3 rows in set (0.00 sec)--6、查询student表中“95031”班或性别为女的记录
-- or表示或者
mysql> select * from student where class='95031' or ssex='女';
+-----+-----------+------+---------------------+-------+
| sno | sname | ssex | sbirthday | class |
+-----+-----------+------+---------------------+-------+
| 102 | 匡明 | 男 | 1972-09-01 00:00:00 | 95031 |
| 103 | 王丽 | 女 | 1974-09-01 00:00:00 | 95033 |
| 105 | 王芳 | 女 | 1976-09-01 00:00:00 | 95031 |
| 106 | 陆君 | 男 | 1978-09-01 00:00:00 | 95031 |
| 108 | 张全蛋 | 男 | 1976-09-01 00:00:00 | 95031 |
| 109 | 赵铁柱 | 男 | 1974-09-01 00:00:00 | 95031 |
+-----+-----------+------+---------------------+-------+
6 rows in set (0.00 sec)--7、以class降序查询student表的所有记录
-- 升序，降序
mysql> select * from student order by class desc;
+-----+-----------+------+---------------------+-------+
| sno | sname | ssex | sbirthday | class |
+-----+-----------+------+---------------------+-------+
| 101 | 曾华 | 男 | 1977-09-01 00:00:00 | 95033 |
| 103 | 王丽 | 女 | 1974-09-01 00:00:00 | 95033 |
| 104 | 李军 | 男 | 1974-09-01 00:00:00 | 95033 |
| 107 | 王尼玛 | 男 | 1975-09-01 00:00:00 | 95033 |
| 102 | 匡明 | 男 | 1972-09-01 00:00:00 | 95031 |
| 105 | 王芳 | 女 | 1976-09-01 00:00:00 | 95031 |
| 106 | 陆君 | 男 | 1978-09-01 00:00:00 | 95031 |
| 108 | 张全蛋 | 男 | 1976-09-01 00:00:00 | 95031 |
| 109 | 赵铁柱 | 男 | 1974-09-01 00:00:00 | 95031 |
+-----+-----------+------+---------------------+-------+
9 rows in set (0.00 sec)-- 默认升序asc;
mysql> select * from student order by class ;
+-----+-----------+------+---------------------+-------+
| sno | sname | ssex | sbirthday | class |
+-----+-----------+------+---------------------+-------+
| 102 | 匡明 | 男 | 1972-09-01 00:00:00 | 95031 |
| 105 | 王芳 | 女 | 1976-09-01 00:00:00 | 95031 |
| 106 | 陆君 | 男 | 1978-09-01 00:00:00 | 95031 |
| 108 | 张全蛋 | 男 | 1976-09-01 00:00:00 | 95031 |
| 109 | 赵铁柱 | 男 | 1974-09-01 00:00:00 | 95031 |
| 101 | 曾华 | 男 | 1977-09-01 00:00:00 | 95033 |
| 103 | 王丽 | 女 | 1974-09-01 00:00:00 | 95033 |
| 104 | 李军 | 男 | 1974-09-01 00:00:00 | 95033 |
| 107 | 王尼玛 | 男 | 1975-09-01 00:00:00 | 95033 |
+-----+-----------+------+---------------------+-------+
9 rows in set (0.00 sec)--8、以cno升序、degree降序查询score表中的所有记录
mysql> select * from score order by cno asc,degree desc;
+-----+-------+--------+
| sno | cno | degree |
+-----+-------+--------+
| 103 | 3-105 | 92 |
| 105 | 3-105 | 88 |
| 109 | 3-105 | 76 |
| 103 | 3-245 | 86 |
| 105 | 3-245 | 75 |
| 109 | 3-245 | 68 |
| 103 | 6-166 | 85 |
| 109 | 6-166 | 81 |
| 105 | 6-166 | 79 |
+-----+-------+--------+
9 rows in set (0.00 sec)--9、查询“95031”班的学生人数
--统计count
mysql> select count(*) from student where class='95031';
+----------+
| count(*) |
+----------+
| 5 |
+----------+
1 row in set (0.00 sec)--10、查询score表中的最高分的学生学号和课程号。（子查询或者排序）
mysql> select sno,cno from score where degree=(select max(degree) from score);
+-----+-------+
| sno | cno |
+-----+-------+
| 103 | 3-105 |
+-----+-------+
1 row in set (0.00 sec)-- 1找最高分
select max(degree) from score-- 2找最高的sno 和 cno
mysql> select sno,cno from score where degree=(select max(degree) from score);-- 排序的做法：
select sno,cno,degree from score order by degree ;mysql> select sno,cno,degree from score order by degree ;
+-----+-------+--------+
| sno | cno | degree |
+-----+-------+--------+
| 109 | 3-245 | 68 |
| 105 | 3-245 | 75 |
| 109 | 3-105 | 76 |
| 105 | 6-166 | 79 |
| 109 | 6-166 | 81 |
| 103 | 6-166 | 85 |
| 103 | 3-245 | 86 |
| 105 | 3-105 | 88 |
| 103 | 3-105 | 92 |
+-----+-------+--------+
9 rows in set (0.01 sec)--select sno,cno,degree from score order by degree desc limit 0,1;
-- limit第一个数字表示从多少开始，第二个数表示查多少条
mysql> select sno,cno,degree from score order by degree desc limit 0,1;
+-----+-------+--------+
| sno | cno | degree |
+-----+-------+--------+
| 103 | 3-105 | 92 |
+-----+-------+--------+
1 row in set (0.00 sec)--11、查询每门课的平均成绩
select * from course;--avg()
select avg(degree) from score where cno='3-105';
select avg(degree) from score where cno='3-245';
select avg(degree) from score where cno='6-166';
select avg(degree) from score where cno='9-888';--我能不能在一个sql 语句中写呢？
--group by 分组
select cno,avg(degree) from score group by cno;mysql> select cno,avg(degree) from score group by cno;
+-------+-------------+
| cno | avg(degree) |
+-------+-------------+
| 3-105 | 85.3333 |
| 3-245 | 76.3333 |
| 6-166 | 81.6667 |
+-------+-------------+
3 rows in set (0.00 sec) --12、查询score表中至少有2名学生选修的并以3开头的课程的平均分数select cno,avg(degree),count(*) from score
group by cno
having count(cno)>=2
and cno like '3%';mysql> select cno,avg(degree),count(*) from score group by cno having count(cno)>=2 and cno like '3%';
+-------+-------------+----------+
| cno | avg(degree) | count(*) |
+-------+-------------+----------+
| 3-105 | 85.3333 | 3 |
| 3-245 | 76.3333 | 3 |
+-------+-------------+----------+
2 rows in set (0.00 sec)-- 13、查询分数大于70，小于90的sno列
select sno,degree from score where degree between 70 and 90;
--where degree>70 and degree<90;mysql> select sno,degree from score where degree between 70 and 90;
+-----+--------+
| sno | degree |
+-----+--------+
| 103 | 86 |
| 103 | 85 |
| 105 | 88 |
| 105 | 75 |
| 105 | 79 |
| 109 | 76 |
| 109 | 81 |
+-----+--------+
7 rows in set (0.00 sec)mysql> select sno,degree from score where degree>70 and degree<90;
+-----+--------+
| sno | degree |
+-----+--------+
| 103 | 86 |
| 103 | 85 |
| 105 | 88 |
| 105 | 75 |
| 105 | 79 |
| 109 | 76 |
| 109 | 81 |
+-----+--------+
7 rows in set (0.00 sec)--14、查询所有学生的 sname、cno 和degree 列
--等号=表存在的 共同字段
select sno,sname from student;mysql> select sno,sname from student;
+-----+-----------+
| sno | sname |
+-----+-----------+
| 101 | 曾华 |
| 102 | 匡明 |
| 103 | 王丽 |
| 104 | 李军 |
| 105 | 王芳 |
| 106 | 陆君 |
| 107 | 王尼玛 |
| 108 | 张全蛋 |
| 109 | 赵铁柱 |
+-----+-----------+
9 rows in set (0.00 sec)select sno,cno,degree from score;mysql> select sno,cno,degree from score;
+-----+-------+--------+
| sno | cno | degree |
+-----+-------+--------+
| 103 | 3-105 | 92 |
| 103 | 3-245 | 86 |
| 103 | 6-166 | 85 |
| 105 | 3-105 | 88 |
| 105 | 3-245 | 75 |
| 105 | 6-166 | 79 |
| 109 | 3-105 | 76 |
| 109 | 3-245 | 68 |
| 109 | 6-166 | 81 |
+-----+-------+--------+
9 rows in set (0.00 sec)select sname,cno,degree from student,score
where student.sno=score.sno;
mysql> select sname,cno,degree from student,score-> where student.sno=score.sno;
+-----------+-------+--------+
| sname | cno | degree |
+-----------+-------+--------+
| 王丽 | 3-105 | 92 |
| 王丽 | 3-245 | 86 |
| 王丽 | 6-166 | 85 |
| 王芳 | 3-105 | 88 |
| 王芳 | 3-245 | 75 |
| 王芳 | 6-166 | 79 |
| 赵铁柱 | 3-105 | 76 |
| 赵铁柱 | 3-245 | 68 |
| 赵铁柱 | 6-166 | 81 |
+-----------+-------+--------+
9 rows in set (0.00 sec)--15、查询所有学生的sno、cname 和degree列
select cno,cname from course;mysql> select cno,cname from course;
+-------+-----------------+
| cno | cname |
+-------+-----------------+
| 3-105 | 计算机导论 |
| 3-245 | 操作系统 |
| 6-166 | 数字电路 |
| 9-888 | 高等数学 |
+-------+-----------------+
4 rows in set (0.01 sec)select cno,sno,degree from score;
mysql> select cno,sno,degree from score;
+-------+-----+--------+
| cno | sno | degree |
+-------+-----+--------+
| 3-105 | 103 | 92 |
| 3-245 | 103 | 86 |
| 6-166 | 103 | 85 |
| 3-105 | 105 | 88 |
| 3-245 | 105 | 75 |
| 6-166 | 105 | 79 |
| 3-105 | 109 | 76 |
| 3-245 | 109 | 68 |
| 6-166 | 109 | 81 |
+-------+-----+--------+
9 rows in set (0.00 sec)select sno,cname,degree from course,score
where course.cno=score.cno;mysql> select sno,cname,degree from course,score-> where course.cno=score.cno;
+-----+-----------------+--------+
| sno | cname | degree |
+-----+-----------------+--------+
| 103 | 计算机导论 | 92 |
| 103 | 操作系统 | 86 |
| 103 | 数字电路 | 85 |
| 105 | 计算机导论 | 88 |
| 105 | 操作系统 | 75 |
| 105 | 数字电路 | 79 |
| 109 | 计算机导论 | 76 |
| 109 | 操作系统 | 68 |
| 109 | 数字电路 | 81 |
+-----+-----------------+--------+
9 rows in set (0.00 sec)--16、查询所有学生的 sname、cname 和degree 列
--sname -> student
--cname ->course
--degree ->score select sname,cname,degree,student.sno as stu_sno,score.sno,course.cno as cou_cno,score.cno from student,course,score
where student.sno=score.sno
and course.cno=score.cno;mysql> select sname,cname,degree from student,course,score-> where student.sno=score.sno and course.cno=score.cno;
+-----------+-----------------+--------+
| sname | cname | degree |
+-----------+-----------------+--------+
| 王丽 | 计算机导论 | 92 |
| 王丽 | 操作系统 | 86 |
| 王丽 | 数字电路 | 85 |
| 王芳 | 计算机导论 | 88 |
| 王芳 | 操作系统 | 75 |
| 王芳 | 数字电路 | 79 |
| 赵铁柱 | 计算机导论 | 76 |
| 赵铁柱 | 操作系统 | 68 |
| 赵铁柱 | 数字电路 | 81 |
+-----------+-----------------+--------+
9 rows in set (0.00 sec)--17、查询“95031”班学生每门课的平均分
select * from student where class='95031';
select sno from student where class='95031';mysql> select * from score where sno in (select sno from student where class='95031');
+-----+-------+--------+
| sno | cno | degree |
+-----+-------+--------+
| 105 | 3-105 | 88 |
| 105 | 3-245 | 75 |
| 105 | 6-166 | 79 |
| 109 | 3-105 | 76 |
| 109 | 3-245 | 68 |
| 109 | 6-166 | 81 |
+-----+-------+--------+
6 rows in set (0.00 sec)select cno,avg(degree)
from score
where sno in (select sno from student where class='95031')
group by cno;mysql> select cno,avg(degree)-> from score-> where sno in (select sno from student where class='95031')-> group by cno;
+-------+-------------+
| cno | avg(degree) |
+-------+-------------+
| 3-105 | 82.0000 |
| 3-245 | 71.5000 |
| 6-166 | 80.0000 |
+-------+-------------+
3 rows in set (0.00 sec)--18、查询选修“3-105”课程的成绩高于“109”号同学“3-105”成绩的所有同学的记录select degree from score where sno='109' and cno='3-105';select * from score where cno='3-105' and degree>(select degree from score where sno='109' and cno='3-105');mysql> select * from score where cno='3-105' and degree>(select degree from score where sno='109' and cno='3-105');
+-----+-------+--------+
| sno | cno | degree |
+-----+-------+--------+
| 103 | 3-105 | 92 |
| 105 | 3-105 | 88 |
+-----+-------+--------+
2 rows in set (0.00 sec)--19、查询成绩高于选修“3-105”课程的成绩高于“109”号同学“3-105”成绩的所有同学的记录
select * from score where degree>(select degree from score where sno='109' and cno='3-105');mysql> select * from score where degree>(select degree from score where sno='109' and cno='3-105');
+-----+-------+--------+
| sno | cno | degree |
+-----+-------+--------+
| 103 | 3-105 | 92 |
| 103 | 3-245 | 86 |
| 103 | 6-166 | 85 |
| 105 | 3-105 | 88 |
| 105 | 6-166 | 79 |
| 109 | 6-166 | 81 |
+-----+-------+--------+--20、查询所有学号为108.101的同学同年出生的所有学生的sno,sname和sbirthday
select * from student where YEAR(sbirthday) in (select YEAR(sbirthday) from student where sno in('101','108'));mysql> select * from student where YEAR(sbirthday) in (select YEAR(sbirthday) from student where sno in('101','108'));
+-----+-----------+------+---------------------+-------+
| sno | sname | ssex | sbirthday | class |
+-----+-----------+------+---------------------+-------+
| 101 | 曾华 | 男 | 1977-09-01 00:00:00 | 95033 |
| 105 | 王芳 | 女 | 1976-09-01 00:00:00 | 95031 |
| 108 | 张全蛋 | 男 | 1976-09-01 00:00:00 | 95031 |
+-----+-----------+------+---------------------+-------+
3 rows in set (0.00 sec)--21、查询 张勋 教师任课的学生的成绩
select * from student
where sno IN (SELECT sno FROM scoreWHERE cno = (SELECT cno FROM course WHERE tno = (SELECT tno FROM teacher WHERE tname='张勋')));mysql> select * from student-> where sno IN (SELECT sno FROM score-> WHERE cno = (SELECT cno FROM course-> WHERE tno = (SELECT tno FROM teacher WHERE tname='张勋')));
+-----+-----------+------+---------------------+-------+
| sno | sname | ssex | sbirthday | class |
+-----+-----------+------+---------------------+-------+
| 103 | 王丽 | 女 | 1974-09-01 00:00:00 | 95033 |
| 105 | 王芳 | 女 | 1976-09-01 00:00:00 | 95031 |
| 109 | 赵铁柱 | 男 | 1974-09-01 00:00:00 | 95031 |
+-----+-----------+------+---------------------+-------+
3 rows in set (0.00 sec)-- 22.查询选修课程的同学人数多余 5 人的教师姓名
SELECT * FROM teacher
WHERE tno IN(SELECT tno FROM course
WHERE cno IN (SELECT cno FROM score GROUP BY cno HAVING COUNT(sno) > 5));--为能查到数据，向score中添加三条数据
INSERT INTO score VALUES('101','3-105','90');
INSERT INTO score VALUES('102','3-105','91');
INSERT INTO score VALUES('104','3-105','89');mysql> SELECT * FROM teacher-> WHERE tno IN(SELECT tno FROM course-> WHERE cno IN (SELECT cno FROM score GROUP BY cno HAVING COUNT(sno) > 5));
+-----+--------+------+---------------------+--------+--------------+
| tno | tname | tsex | sbirthday | prof | depart |
+-----+--------+------+---------------------+--------+--------------+
| 825 | 王萍 | 女 | 1972-06-13 00:00:00 | 助教 | 计算机系 |
+-----+--------+------+---------------------+--------+--------------+
1 row in set (0.00 sec)-- 23.查询95033班和95031班全体学生的记录
SELECT * FROM student WHERE class IN('95031','95033') ORDER BY class ;mysql> SELECT * FROM student WHERE class IN('95031','95033') ORDER BY class ;
+-----+-----------+------+---------------------+-------+
| sno | sname | ssex | sbirthday | class |
+-----+-----------+------+---------------------+-------+
| 102 | 匡明 | 男 | 1972-09-01 00:00:00 | 95031 |
| 105 | 王芳 | 女 | 1976-09-01 00:00:00 | 95031 |
| 106 | 陆君 | 男 | 1978-09-01 00:00:00 | 95031 |
| 108 | 张全蛋 | 男 | 1976-09-01 00:00:00 | 95031 |
| 109 | 赵铁柱 | 男 | 1974-09-01 00:00:00 | 95031 |
| 101 | 曾华 | 男 | 1977-09-01 00:00:00 | 95033 |
| 103 | 王丽 | 女 | 1974-09-01 00:00:00 | 95033 |
| 104 | 李军 | 男 | 1974-09-01 00:00:00 | 95033 |
| 107 | 王尼玛 | 男 | 1975-09-01 00:00:00 | 95033 |
+-----+-----------+------+---------------------+-------+
9 rows in set (0.00 sec)-- 24.查询存在85分以上成绩的课程cno
SELECT * FROM score where degree > 85;mysql> SELECT * FROM score where degree > 85;
+-----+-------+--------+
| sno | cno | degree |
+-----+-------+--------+
| 101 | 3-105 | 90 |
| 102 | 3-105 | 91 |
| 103 | 3-105 | 92 |
| 103 | 3-245 | 86 |
| 104 | 3-105 | 89 |
| 105 | 3-105 | 88 |
+-----+-------+--------+
6 rows in set (0.00 sec)-- 25.查出所有'计算机系' 教师所教课程的成绩表
SELECT * FROM score WHERE cno IN (SELECT cno FROM course
WHERE tno IN (SELECT tno FROM teacher
WHERE depart = '计算机系'));mysql> SELECT * FROM score WHERE cno IN (SELECT cno FROM course-> WHERE tno IN (SELECT tno FROM teacher-> WHERE depart = '计算机系'));
+-----+-------+--------+
| sno | cno | degree |
+-----+-------+--------+
| 103 | 3-245 | 86 |
| 105 | 3-245 | 75 |
| 109 | 3-245 | 68 |
| 101 | 3-105 | 90 |
| 102 | 3-105 | 91 |
| 103 | 3-105 | 92 |
| 104 | 3-105 | 89 |
| 105 | 3-105 | 88 |
| 109 | 3-105 | 76 |
+-----+-------+--------+
9 rows in set (0.00 sec)-- 26.查询'计算机系'与'电子工程系' 不同职称的教师的name和prof
-- UNION 求并集
SELECT * FROM teacher WHERE depart = '计算机系' AND prof NOT IN (SELECT prof FROM teacher WHERE depart = '电子工程系')
UNION
SELECT * FROM teacher WHERE depart = '电子工程系' AND prof NOT IN (SELECT prof FROM teacher WHERE depart = '计算机系');mysql> SELECT * FROM teacher WHERE depart = '计算机系' AND prof NOT IN (SELECT prof FROM teacher WHERE depart = '电子工 程系')-> UNION-> SELECT * FROM teacher WHERE depart = '电子工程系' AND prof NOT IN (SELECT prof FROM teacher WHERE depart = '计算 机系');
+-----+--------+------+---------------------+-----------+-----------------+
| tno | tname | tsex | sbirthday | prof | depart |
+-----+--------+------+---------------------+-----------+-----------------+
| 804 | 李成 | 男 | 1958-12-02 00:00:00 | 副教授 | 计算机系 |
| 856 | 张勋 | 男 | 1969-09-18 00:00:00 | 讲师 | 电子工程系 |
+-----+--------+------+---------------------+-----------+-----------------+
2 rows in set (0.00 sec)-- 27, 查询选修编号为"3-105"课程且成绩至少高于选修编号为'3-245'同学的cno,sno和degree,并且按照degree从高到地次序排序
-- 至少表示大于其中 至少一个，any
select * from score where cno = '3-105'
AND degree > ANY(SELECT degree FROM score WHERE cno = '3-245' )
ORDER BY degree desc ;mysql> select * from score where cno = '3-105' AND degree > ANY(SELECT degree FROM score WHERE cno = '3-245' ) ORDER BY degree desc ;
+-----+-------+--------+
| sno | cno | degree |
+-----+-------+--------+
| 103 | 3-105 | 92 |
| 102 | 3-105 | 91 |
| 101 | 3-105 | 90 |
| 104 | 3-105 | 89 |
| 105 | 3-105 | 88 |
| 109 | 3-105 | 76 |
+-----+-------+--------+
6 rows in set (0.00 sec)-- 28.查询选修编号为"3-105"且成绩高于选修编号为"3-245"课程的同学cno,sno和degree
-- 且？
SELECT * FROM score WHERE degree > ALL (select degree from score WHERE cno = '3-245') AND cno = '3-105';mysql> SELECT * FROM score WHERE degree > ALL (select degree from score WHERE cno = '3-245') AND cno = '3-105';
+-----+-------+--------+
| sno | cno | degree |
+-----+-------+--------+
| 101 | 3-105 | 90 |
| 102 | 3-105 | 91 |
| 103 | 3-105 | 92 |
| 104 | 3-105 | 89 |
| 105 | 3-105 | 88 |
+-----+-------+--------+
5 rows in set (0.00 sec)-- 29. 查询所有教师和同学的 name ,sex, birthday
-- 别名？ as,后面的数据默认使用别名为列名
SELECT sname AS name, ssex AS sex, sbirthday AS birthday FROM student
UNION
SELECT tname , tsex , tbirthday FROM teacher;mysql> SELECT sname AS name, ssex AS sex, sbirthday AS birthday FROM student-> UNION-> SELECT tname , tsex , tbirthday FROM teacher;
+-----------+-----+---------------------+
| name | sex | birthday |
+-----------+-----+---------------------+
| 曾华 | 男 | 1977-09-01 00:00:00 |
| 匡明 | 男 | 1972-09-01 00:00:00 |
| 王丽 | 女 | 1974-09-01 00:00:00 |
| 李军 | 男 | 1974-09-01 00:00:00 |
| 王芳 | 女 | 1976-09-01 00:00:00 |
| 陆君 | 男 | 1978-09-01 00:00:00 |
| 王尼玛 | 男 | 1975-09-01 00:00:00 |
| 张全蛋 | 男 | 1976-09-01 00:00:00 |
| 赵铁柱 | 男 | 1974-09-01 00:00:00 |
| 李成 | 男 | 1958-12-02 00:00:00 |
| 王萍 | 女 | 1972-06-13 00:00:00 |
| 刘冰 | 女 | 1986-10-10 00:00:00 |
| 张勋 | 男 | 1969-09-18 00:00:00 |
+-----------+-----+---------------------+
13 rows in set (0.00 sec)-- 30.查询所有'女'教师和'女'学生的name,sex,birthday
SELECT sname AS name, ssex AS sex, sbirthday AS birthday FROM student WHERE ssex = '女'
UNION
SELECT tname AS name, tsex AS sex, tbirthday AS birthday FROM teacher WHERE tsex = '女';mysql> SELECT sname AS name, ssex AS sex, sbirthday AS birthday FROM student WHERE ssex = '女'-> UNION-> SELECT tname AS name, tsex AS sex, tbirthday AS birthday FROM teacher WHERE tsex = '女';
+--------+-----+---------------------+
| name | sex | birthday |
+--------+-----+---------------------+
| 王丽 | 女 | 1974-09-01 00:00:00 |
| 王芳 | 女 | 1976-09-01 00:00:00 |
| 王萍 | 女 | 1972-06-13 00:00:00 |
| 刘冰 | 女 | 1986-10-10 00:00:00 |
+--------+-----+---------------------+
4 rows in set (0.00 sec)-- 31.查询成绩比该课程平均成绩低的同学的成绩表
select * from score;
a(sc1) b(sc2)
+-----+-------+--------+ +-----+-------+--------+
| sno | cno | degree | | sno | cno | degree |
+-----+-------+--------+ +-----+-------+--------+
| 101 | 3-105 | 90 | | 101 | 3-105 | 90 |
| 102 | 3-105 | 91 | | 102 | 3-105 | 91 |
| 103 | 3-105 | 92 | | 103 | 3-105 | 92 |
| 103 | 3-245 | 86 | | 103 | 3-245 | 86 |
| 103 | 6-166 | 85 | | 103 | 6-166 | 85 |
| 104 | 3-105 | 89 | | 104 | 3-105 | 89 |
| 105 | 3-105 | 88 | | 105 | 3-105 | 88 |
| 105 | 3-245 | 75 | | 105 | 3-245 | 75 |
| 105 | 6-166 | 79 | | 105 | 6-166 | 79 |
| 109 | 3-105 | 76 | | 109 | 3-105 | 76 |
| 109 | 3-245 | 68 | | 109 | 3-245 | 68 |
| 109 | 6-166 | 81 | | 109 | 6-166 | 81 |
+-----+-------+--------+ +-----+-------+--------+
12 rows in set (0.00 sec)
SELECT * FROM score AS sc1 WHERE sc1.degree < (SELECT AVG(degree) FROM score AS sc2 WHERE sc1.cno = sc2.cno);mysql> SELECT * FROM score AS sc1 WHERE sc1.degree < (SELECT AVG(degree) FROM score AS sc2 WHERE sc1.cno = sc2.cno);
+-----+-------+--------+
| sno | cno | degree |
+-----+-------+--------+
| 105 | 3-245 | 75 |
| 105 | 6-166 | 79 |
| 109 | 3-105 | 76 |
| 109 | 3-245 | 68 |
| 109 | 6-166 | 81 |
+-----+-------+--------+
5 rows in set (0.00 sec)-- 32.查询所有任课教师的tname 和 depart(要在分数表中可以查得到，排了课)-- 课程表中安排了课程
SELECT * FROM teacher WHERE tno IN(SELECT tno FROM course);mysql> SELECT * FROM teacher WHERE tno IN(SELECT tno FROM course);
+-----+--------+------+---------------------+-----------+-----------------+
| tno | tname | tsex | tbirthday | prof | depart |
+-----+--------+------+---------------------+-----------+-----------------+
| 804 | 李成 | 男 | 1958-12-02 00:00:00 | 副教授 | 计算机系 |
| 825 | 王萍 | 女 | 1972-06-13 00:00:00 | 助教 | 计算机系 |
| 831 | 刘冰 | 女 | 1986-10-10 00:00:00 | 助教 | 电子工程系 |
| 856 | 张勋 | 男 | 1969-09-18 00:00:00 | 讲师 | 电子工程系 |
+-----+--------+------+---------------------+-----------+-----------------+
4 rows in set (0.00 sec)-- 33.查出至少有2名男生的班号
-- 为更好看出向学生表 添加一条数据
insert into student values('110','张飞','男','1977-01-29','95038');
SELECT class FROM student WHERE ssex = '男' GROUP BY class HAVING COUNT(*) > 1; --或者COUNT(sno) > 1mysql> SELECT class FROM student WHERE ssex = '男' GROUP BY class HAVING COUNT(*) > 1;
+-------+
| class |
+-------+
| 95031 |
| 95033 |
+-------+
2 rows in set (0.00 sec)-- 34.查询student 表中 不姓"王"的同学的记录
-- 模糊查询筛选 not like
SELECT * FROM student WHERE sname NOT LIKE '王%'; mysql> SELECT * FROM student WHERE sname NOT LIKE '王%';
+-----+-----------+------+---------------------+-------+
| sno | sname | ssex | sbirthday | class |
+-----+-----------+------+---------------------+-------+
| 101 | 曾华 | 男 | 1977-09-01 00:00:00 | 95033 |
| 102 | 匡明 | 男 | 1972-09-01 00:00:00 | 95031 |
| 104 | 李军 | 男 | 1974-09-01 00:00:00 | 95033 |
| 106 | 陆君 | 男 | 1978-09-01 00:00:00 | 95031 |
| 108 | 张全蛋 | 男 | 1976-09-01 00:00:00 | 95031 |
| 109 | 赵铁柱 | 男 | 1974-09-01 00:00:00 | 95031 |
+-----+-----------+------+---------------------+-------+
6 rows in set (0.00 sec)-- 35. 查询student 中每个学生的姓名和年龄(当前时间 - 出生年份)
SELECT sname, YEAR(NOW()) - YEAR(sbirthday) AS '年龄' FROM student;mysql> SELECT sname, YEAR(NOW()) - YEAR(sbirthday) AS '年龄' FROM student;
+-----------+--------+
| sname | 年龄 |
+-----------+--------+
| 曾华 | 43 |
| 匡明 | 48 |
| 王丽 | 46 |
| 李军 | 46 |
| 王芳 | 44 |
| 陆君 | 42 |
| 王尼玛 | 45 |
| 张全蛋 | 44 |
| 赵铁柱 | 46 |
| 张飞 | 43 |
+-----------+--------+
10 rows in set (0.00 sec)-- 36. 查询student中最大和最小的 sbirthday的值
-- max min
SELECT MAX(sbirthday) as '最大',MIN(sbirthday) as '最小' FROM student;mysql> SELECT MAX(sbirthday) as '最大',MIN(sbirthday) as '最小' FROM student;
+---------------------+---------------------+
| 最大 | 最小 |
+---------------------+---------------------+
| 1978-09-01 00:00:00 | 1972-09-01 00:00:00 |
+---------------------+---------------------+
1 row in set (0.00 sec)-- 37.以班级号和年龄从大到小的顺序查询student表中的全部记录
SELECt * FROM student ORDER BY class DESC, sbirthday; mysql> SELECt * FROM student ORDER BY class DESC, sbirthday;
+-----+-----------+------+---------------------+-------+
| sno | sname | ssex | sbirthday | class |
+-----+-----------+------+---------------------+-------+
| 103 | 王丽 | 女 | 1974-09-01 00:00:00 | 95033 |
| 104 | 李军 | 男 | 1974-09-01 00:00:00 | 95033 |
| 107 | 王尼玛 | 男 | 1975-09-01 00:00:00 | 95033 |
| 101 | 曾华 | 男 | 1977-09-01 00:00:00 | 95033 |
| 102 | 匡明 | 男 | 1972-09-01 00:00:00 | 95031 |
| 109 | 赵铁柱 | 男 | 1974-09-01 00:00:00 | 95031 |
| 105 | 王芳 | 女 | 1976-09-01 00:00:00 | 95031 |
| 108 | 张全蛋 | 男 | 1976-09-01 00:00:00 | 95031 |
| 106 | 陆君 | 男 | 1978-09-01 00:00:00 | 95031 |
+-----+-----------+------+---------------------+-------+
9 rows in set (0.00 sec)-- 38.查询"男"教师 及其所上的课
SELECT * FROM course WHERE tno IN (SELECT tno FROM teacher WHERE tsex = '男');mysql> SELECT * FROM course WHERE tno IN (SELECT tno FROM teacher WHERE tsex = '男');
+-------+--------------+-----+
| cno | cname | tno |
+-------+--------------+-----+
| 3-245 | 操作系统 | 804 |
| 6-166 | 数字电路 | 856 |
+-------+--------------+-----+
2 rows in set (0.00 sec)-- 39.查询最高分同学的sno ,cno 和 degree;
SELECT * FROM score WHERE degree = (select MAX(degree) AS degree FROM score);mysql> SELECT * FROM score WHERE degree = (select MAX(degree) AS degree FROM score);
+-----+-------+--------+
| sno | cno | degree |
+-----+-------+--------+
| 103 | 3-105 | 92 |
+-----+-------+--------+
1 row in set (0.00 sec)-- 40. 查询和"李军"同性别的所有同学的sname
SELECT sname, ssex FROM student WHERE sSEX = (SELECT ssex FROM student WHERE sname = '李军');mysql> SELECT sname, ssex FROM student WHERE sSEX = (SELECT ssex FROM student WHERE sname = '李军');
+-----------+------+
| sname | ssex |
+-----------+------+
| 曾华 | 男 |
| 匡明 | 男 |
| 李军 | 男 |
| 陆君 | 男 |
| 王尼玛 | 男 |
| 张全蛋 | 男 |
| 赵铁柱 | 男 |
+-----------+------+
7 rows in set (0.00 sec)-- 41.查询和"李军"同性别并且同班的所有同学的sname
SELECT sname, ssex FROM student
WHERE ssex = (SELECT ssex FROM student WHERE sname = '李军')
AND class = (SELECT class FROM student WHERE sname = '李军');mysql> SELECT sname, ssex FROM student WHERE ssex = (SELECT ssex FROM student WHERE sname = '李军') AND class = (SELECT class FROM student WHERE sname = '李军');
+-----------+------+
| sname | ssex |
+-----------+------+
| 曾华 | 男 |
| 李军 | 男 |
| 王尼玛 | 男 |
+-----------+------+
3 rows in set (0.00 sec)-- 42. 查询所有选修'计算机导论'课程的'男'同学的成绩表
SELECT * FROM score
WHERE cno = (SELECT cno FROM course WHERE cname = '计算机导论' )
AND sno IN(SELECT sno FROM student WHERE ssex = '男');mysql> SELECT * FROM score WHERE cno = (SELECT cno FROM course WHERE cname = '计算机导论' ) AND sno IN(SELECT sno FROM student WHERE ssex = '男');
+-----+-------+--------+
| sno | cno | degree |
+-----+-------+--------+
| 101 | 3-105 | 90 |
| 102 | 3-105 | 91 |
| 104 | 3-105 | 89 |
| 109 | 3-105 | 76 |
+-----+-------+--------+
4 rows in set (0.00 sec)-- 43. 假设使用了以下命令建立了一个grade表：
CREATE TABLE grade(low INT(3),upp INT(3),grade CHAR(1)
);INSERT INTO grade VALUES(90,100,'A');
INSERT INTO grade VALUES(80,89,'B');
INSERT INTO grade VALUES(70,79,'c');
INSERT INTO grade VALUES(60,69,'D');
INSERT INTO grade VALUES(0,59,'E');-- 现查询所有同学的sno , cno 和grade列
SELECT sno, cno , grade FROM score, grade WHERE degree BETWEEN low and upp; mysql> SELECT sno, cno , grade FROM score, grade WHERE degree BETWEEN low and upp;
+-----+-------+-------+
| sno | cno | grade |
+-----+-------+-------+
| 101 | 3-105 | A |
| 102 | 3-105 | A |
| 103 | 3-105 | A |
| 103 | 3-245 | B |
| 103 | 6-166 | B |
| 104 | 3-105 | B |
| 105 | 3-105 | B |
| 105 | 3-245 | c |
| 105 | 6-166 | c |
| 109 | 3-105 | c |
| 109 | 3-245 | D |
| 109 | 6-166 | B |
+-----+-------+-------+
12 rows in set (0.00 sec)
select * from grade;-- 将某行的c换为C
UPDATE grade SET grade = REPLACE (grade, 'c', 'C');第四章 mysql连接查询
SQL 的四种连接查询内连接
inner join或join外连接
1.左连接 left join 或者 left outer join2.右连接 right join 或者 right outer join3.完全外连接 full join 或者 full outer join-- 创建两张表-- person 表
id,
name,
cardId create table person(id int,name varchar(20),cardId int
);-- card表
id,
namecreate table card(id int,name varchar(20)
);insert into card values(1,'饭卡');
insert into card values(2,'建行卡');
insert into card values(3,'工商卡');
insert into card values(4,'邮政卡');
insert into card values(5,'农行卡');insert into person values(1,'张三',1);
insert into person values(2,'李四',3);
insert into person values(3,'王五',6);-- 并没有创建外键-- 1、inner join 查询（内连接）select * from person inner join card on person.cardId=card.id;mysql> select * from person inner join card on person.cardId=card.id;
+------+--------+--------+------+-----------+
| id | name | cardId | id | name |
+------+--------+--------+------+-----------+
| 1 | 张三 | 1 | 1 | 饭卡 |
| 2 | 李四 | 3 | 3 | 工商卡 |
+------+--------+--------+------+-----------+
2 rows in set (0.00 sec)-- 内连查询，其实就是两表数据 ，通过某个字段相等， 查询出相关记录数据。-- 2、left join(左外连接)
select * from person left join card on person.cardId=card.id;mysql> select * from person left join card on person.cardId=card.id;
+------+--------+--------+------+-----------+
| id | name | cardId | id | name |
+------+--------+--------+------+-----------+
| 1 | 张三 | 1 | 1 | 饭卡 |
| 2 | 李四 | 3 | 3 | 工商卡 |
| 3 | 王五 | 6 | NULL | NULL |
+------+--------+--------+------+-----------+
3 rows in set (0.00 sec)-- 左外连接， 会把左边表里面的所有数据取出来， 而右边表中的数据 ，如果由相等的， 就显示出来。
-- 如果没有， 就会补 NULL
select * from person left OUTER join card on person.cardId=card.id;mysql> select * from person left OUTER join card on person.cardId=card.id;
+------+--------+--------+------+-----------+
| id | name | cardId | id | name |
+------+--------+--------+------+-----------+
| 1 | 张三 | 1 | 1 | 饭卡 |
| 2 | 李四 | 3 | 3 | 工商卡 |
| 3 | 王五 | 6 | NULL | NULL |
+------+--------+--------+------+-----------+
3 rows in set (0.00 sec)-- 3、right join(右外连接)
select * from person right join card on person.cardId=card.id;mysql> select * from person right join card on person.cardId=card.id;
+------+--------+--------+------+-----------+
| id | name | cardId | id | name |
+------+--------+--------+------+-----------+
| 1 | 张三 | 1 | 1 | 饭卡 |
| 2 | 李四 | 3 | 3 | 工商卡 |
| NULL | NULL | NULL | 2 | 建行卡 |
| NULL | NULL | NULL | 4 | 邮政卡 |
| NULL | NULL | NULL | 5 | 农行卡 |
+------+--------+--------+------+-----------+
5 rows in set (0.00 sec)-- 右外连接， 会把右边表里面的所有数据取出来， 而左边表中的数据 ，如果由相等的， 就显示出来。
-- 如果没有， 就会补 NULLselect * from person right OUTER join card on person.cardId=card.id;mysql> select * from person right OUTER join card on person.cardId=card.id;
+------+--------+--------+------+-----------+
| id | name | cardId | id | name |
+------+--------+--------+------+-----------+
| 1 | 张三 | 1 | 1 | 饭卡 |
| 2 | 李四 | 3 | 3 | 工商卡 |
| NULL | NULL | NULL | 2 | 建行卡 |
| NULL | NULL | NULL | 4 | 邮政卡 |
| NULL | NULL | NULL | 5 | 农行卡 |
+------+--------+--------+------+-----------+
5 rows in set (0.00 sec)-- 4、全外连接
select * from person full join card on person.cardId=card.id;-- mysql 不支持 full joinselect * from person left join card on person.cardId=card.id
union
select * from person right join card on person.cardId=card.id;第五章 mysql事务
--mysql 事务mysql 中，事务其实是一个最小的不可分割的工作单元 。事务能保证一个业务的完整性。比如我们的 银行转账：a-> -100update user set money=money-100 where name = 'a';b-> +100update user set money=money-100 where name = 'b';-- 实际程序中，如果只有一条语句执行成功了，而另一条没有执行成功？
-- 出现数据前后不一致。update user set money=money-100 where name = 'a';update user set money=money-100 where name = 'b';-- 多条sql语句，可能会有同时成功的要求， 要么就同时失败。-- mysql 中如何控制事务？1、mysql 默认是开启事务的。（视频有误，自动提交关闭才是事务开启） mysql> select @@autocommit;
+--------------+
| @@autocommit |
+--------------+
| 1 |
+--------------+
1 row in set (0.01 sec)-- 默认事务开启的作用是什么？
-- 当我们去执行一个sql 语句的时候，效果会立马体现出来，且不能回滚。create database bank;create table user(id int primary key,name varchar(20),money int
);insert into user values(1,'a',1000);-- 事务回滚： 撤销mysql语句执行效果
rollback;mysql> rollback;
Query OK, 0 rows affected (0.00 sec)mysql> select * from user;
+----+------+-------+
| id | name | money |
+----+------+-------+
| 1 | a | 1000 |
+----+------+-------+
1 row in set (0.00 sec)-- 设置mysql 自动提交为 false
set autocommit =0;mysql> set autocommit =0;
Query OK, 0 rows affected (0.01 sec)mysql> select @@autocommit;
+--------------+
| @@autocommit |
+--------------+
| 0 |
+--------------+
1 row in set (0.00 sec)--上面的操作 ，关闭了mysql 的自动提交(commit)insert into user values(2,'b',1000);mysql> insert into user values(2,'b',1000);
Query OK, 1 row affected (0.00 sec)mysql> select * from user;
+----+------+-------+
| id | name | money |
+----+------+-------+
| 1 | a | 1000 |
| 2 | b | 1000 |
+----+------+-------+
2 rows in set (0.00 sec)mysql> rollback;
Query OK, 0 rows affected (0.00 sec)mysql> select * from user;
+----+------+-------+
| id | name | money |
+----+------+-------+
| 1 | a | 1000 |
+----+------+-------+
1 row in set (0.00 sec)-- 再一次插入数据
mysql> insert into user values(2,'b',1000);
Query OK, 1 row affected (0.00 sec)-- 手动提交数据
mysql> commit;
Query OK, 0 rows affected (0.01 sec)-- 再撤销，是不可撤销的（持久性）
mysql> rollback;
Query OK, 0 rows affected (0.00 sec)mysql> select * from user;
+----+------+-------+
| id | name | money |
+----+------+-------+
| 1 | a | 1000 |
| 2 | b | 1000 |
+----+------+-------+
2 rows in set (0.00 sec)-- 自动提交？ @@autocommit=1；
-- 手动提交？ commit;
-- 事务回滚？ rollback;-- 如果说这个时候转账：update user set money=money-100 where name = 'a';
update user set money=money+100 where name = 'b';rollback;mysql> update user set money=money-100 where name = 'a';
Query OK, 1 row affected (0.00 sec)
Rows matched: 1 Changed: 1 Warnings: 0mysql> update user set money=money+100 where name = 'b';
Query OK, 1 row affected (0.00 sec)
Rows matched: 1 Changed: 1 Warnings: 0mysql> select * from user;
+----+------+-------+
| id | name | money |
+----+------+-------+
| 1 | a | 900 |
| 2 | b | 1100 |
+----+------+-------+
2 rows in set (0.00 sec)mysql> rollback;
Query OK, 0 rows affected (0.01 sec)mysql> select * from user;
+----+------+-------+
| id | name | money |
+----+------+-------+
| 1 | a | 1000 |
| 2 | b | 1000 |
+----+------+-------+
2 rows in set (0.00 sec)-- 事务给我们提供一个返回的机会。set autocommit =1;mysql> set autocommit =1;
Query OK, 0 rows affected (0.00 sec)mysql> select @@autocommit;
+--------------+
| @@autocommit |
+--------------+
| 1 |
+--------------+
1 row in set (0.00 sec)begin;
-- 或者
start transaction;
-- 都可以帮我们手动开启一个事务mysql> update user set money=money-100 where name = 'a';
Query OK, 1 row affected (0.01 sec)
Rows matched: 1 Changed: 1 Warnings: 0mysql> update user set money=money+100 where name = 'b';
Query OK, 1 row affected (0.01 sec)
Rows matched: 1 Changed: 1 Warnings: 0mysql> select * from user;
+----+------+-------+
| id | name | money |
+----+------+-------+
| 1 | a | 900 |
| 2 | b | 1100 |
+----+------+-------+
2 rows in set (0.00 sec)-- 事务回滚：
mysql> rollback;
Query OK, 0 rows affected (0.00 sec)-- 没有被撤销
mysql> select * from user;
+----+------+-------+
| id | name | money |
+----+------+-------+
| 1 | a | 900 |
| 2 | b | 1100 |
+----+------+-------+
2 rows in set (0.00 sec)-- 手动开启事务（1）
begin;
update user set money=money-100 where name = 'a';
update user set money=money+100 where name = 'b';mysql> begin;
Query OK, 0 rows affected (0.00 sec)mysql> update user set money=money-100 where name = 'a';
Query OK, 1 row affected (0.01 sec)
Rows matched: 1 Changed: 1 Warnings: 0mysql> update user set money=money+100 where name = 'b';
Query OK, 1 row affected (0.00 sec)
Rows matched: 1 Changed: 1 Warnings: 0mysql> select * from user;
+----+------+-------+
| id | name | money |
+----+------+-------+
| 1 | a | 800 |
| 2 | b | 1200 |
+----+------+-------+
2 rows in set (0.00 sec)mysql> rollback;
Query OK, 0 rows affected (0.00 sec)mysql> select * from user;
+----+------+-------+
| id | name | money |
+----+------+-------+
| 1 | a | 900 |
| 2 | b | 1100 |
+----+------+-------+
2 rows in set (0.00 sec)-- 手动开启事务（2）
-- 事务开启之后 ，一旦 commit提交，就不可以回滚 （也就是当前的事务在提交的时候就结束了）
start transaction;
update user set money=money-100 where name = 'a';
update user set money=money+100 where name = 'b';mysql> start transaction;
Query OK, 0 rows affected (0.00 sec)mysql> update user set money=money-100 where name = 'a';
Query OK, 1 row affected (0.00 sec)
Rows matched: 1 Changed: 1 Warnings: 0mysql> update user set money=money+100 where name = 'b';
Query OK, 1 row affected (0.00 sec)
Rows matched: 1 Changed: 1 Warnings: 0mysql> select * from user;
+----+------+-------+
| id | name | money |
+----+------+-------+
| 1 | a | 800 |
| 2 | b | 1200 |
+----+------+-------+
2 rows in set (0.00 sec)mysql> rollback;
Query OK, 0 rows affected (0.00 sec)mysql> select * from user;
+----+------+-------+
| id | name | money |
+----+------+-------+
| 1 | a | 900 |
| 2 | b | 1100 |
+----+------+-------+
2 rows in set (0.00 sec)mysql> commit;
Query OK, 0 rows affected (0.00 sec)mysql> select * from user;
+----+------+-------+
| id | name | money |
+----+------+-------+
| 1 | a | 900 |
| 2 | b | 1100 |
+----+------+-------+
2 rows in set (0.00 sec)mysql> rollback;
Query OK, 0 rows affected (0.00 sec)mysql> select * from user;
+----+------+-------+
| id | name | money |
+----+------+-------+
| 1 | a | 900 |
| 2 | b | 1100 |
+----+------+-------+
2 rows in set (0.00 sec)事务的四大特征
A 原子性：事务是最小的
C 一致性：事务要求，同一事物中的sql语句，必须保证同时成功或同时失败
I 隔离性：事务1和事务2 之间是具有隔离性
D 持久性：事务一旦结束(commit ,rollback)，就不可能返回事务的开启：1.修改默认提交 set autocommit=02. begin;3. start transaction;事务手动提交：commit;事务手动回滚： rollback;-- 事务的隔离性:1、read uncommitted; 读未提交
2、read committed; 读已经提交的
3、repeatable read; 可以重复读
4、serializable; 串行化1-read uncommitted如果有事务a, 事务b
a 事务对事务进行操作， 在操作过程中， 事务没有被提交， 但是b可以看见a 操作的结果bank数据库 user表
insert into user values(3,'小明',1000);
insert into user values(4,'淘宝店',1000);mysql> select * from user;
+----+-----------+-------+
| id | name | money |
+----+-----------+-------+
| 1 | a | 900 |
| 2 | b | 1100 |
| 3 | 小明 | 1000 |
| 4 | 淘宝店 | 1000 |
+----+-----------+-------+
4 rows in set (0.00 sec)-- 如何查看数据库的隔离级别？
mysql 8.0:
-- 系统级别的
select @@global.transaction_isolation;
-- 会话级别的
select @@transaction_isolation;-- mysql 默认隔离级别 REPEATABLE-READ
mysql> select @@global.transaction_isolation;
+--------------------------------+
| @@global.transaction_isolation |
+--------------------------------+
| REPEATABLE-READ |
+--------------------------------+
1 row in set (0.01 sec)mysql 5.x:
select @@global.tx_isolation;
select @@tx_isolation;-- 如何修改隔离级别？set global transaction isolation level read uncommitted;mysql> set global transaction isolation level read uncommitted;
Query OK, 0 rows affected (0.02 sec)mysql> select @@global.transaction_isolation;
+--------------------------------+
| @@global.transaction_isolation |
+--------------------------------+
| READ-UNCOMMITTED |
+--------------------------------+
1 row in set (0.00 sec)-- 转账：小明在淘宝店买鞋子：800块钱，小明-》成都 ATM淘宝店-》广州 ATMstart transaction;
update user set money=money-800 where name='小明';
update user set money=money+800 where name='淘宝店';mysql> start transaction;
Query OK, 0 rows affected (0.00 sec)mysql> update user set money=money-800 where name='小明';
Query OK, 1 row affected (0.00 sec)
Rows matched: 1 Changed: 1 Warnings: 0mysql> update user set money=money+800 where name='淘宝店';
Query OK, 1 row affected (0.00 sec)
Rows matched: 1 Changed: 1 Warnings: 0-- 给淘宝店打电话，说你查一下，是不是到账了-- 淘宝店在广州查账
mysql> select * from user;
+----+-----------+-------+
| id | name | money |
+----+-----------+-------+
| 1 | a | 900 |
| 2 | b | 1100 |
| 3 | 小明 | 200 |
| 4 | 淘宝店 | 1800 |
+----+-----------+-------+
4 rows in set (0.00 sec)-- 发货
-- 晚上请女朋友吃好吃的
--1800-- 小明-》成都
mysql> rollback;
Query OK, 0 rows affected (0.01 sec)mysql> select * from user;
+----+-----------+-------+
| id | name | money |
+----+-----------+-------+
| 1 | a | 900 |
| 2 | b | 1100 |
| 3 | 小明 | 1000 |
| 4 | 淘宝店 | 1000 |
+----+-----------+-------+
4 rows in set (0.00 sec)-- 结账的时候发现钱不够
mysql> select * from user;
+----+-----------+-------+
| id | name | money |
+----+-----------+-------+
| 1 | a | 900 |
| 2 | b | 1100 |
| 3 | 小明 | 1000 |
| 4 | 淘宝店 | 1000 |
+----+-----------+-------+
4 rows in set (0.00 sec)-- 如果两个不同的地方，都在进行操作，如果事务a 开启之后，他的数据可以被其他事务读取到。
-- 这样会出现（脏读）
-- 脏读：一个事务读到了另外一个事务没有提交的数据，就叫做脏读。
-- 实际开发是不允许脏读出现的。2-read committed; 读已经提交的set global transaction isolation level read committed;select @@global.transaction_isolation;-- 修改隔离级别为read committed
mysql> select @@global.transaction_isolation;
+--------------------------------+
| @@global.transaction_isolation |
+--------------------------------+
| READ-COMMITTED |
+--------------------------------+
1 row in set (0.00 sec)bank 数据库 user表小张：银行的会计
start transaction;
select * from user;
+----+-----------+-------+
| id | name | money |
+----+-----------+-------+
| 1 | a | 900 |
| 2 | b | 1100 |
| 3 | 小明 | 1000 |
| 4 | 淘宝店 | 1000 |
+----+-----------+-------+
4 rows in set (0.00 sec)小张出去上厕所去了。。。抽烟小王：
start transaction;
insert into user values(5,'c',100);
commit;+----+-----------+-------+
| id | name | money |
+----+-----------+-------+
| 1 | a | 900 |
| 2 | b | 1100 |
| 3 | 小明 | 1000 |
| 4 | 淘宝店 | 1000 |
| 5 | c | 100 |
+----+-----------+-------+
5 rows in set (0.00 sec)-- 小张上完厕所， 抽完烟回来了
select avg(money) from user;
+------------+
| avg(money) |
+------------+
| 820.0000 |
+------------+
1 row in set (0.01 sec)-- money 的平均值不是1000，变少了？-- 虽然我只能读到另一个事务提交的数据，但还是会出现问题，就是
-- 读取同一个表的数据， 发现前后不一致
-- 不可重复读现象：read committed3、repeatable read; 可以重复读set global transaction isolation level repeatable read;select @@global.transaction_isolation;
+--------------------------------+
| @@global.transaction_isolation |
+--------------------------------+
| REPEATABLE-READ |
+--------------------------------+
1 row in set (0.00 sec)-- 在REPEATABLE-READ 隔离级别下又会出现什么问题？
select * from user;-- 张全蛋-成都
start transaction;-- 王尼玛-北京
start transaction;-- 张全蛋-成都
mysql> insert into user values(6,'d',1000);
Query OK, 1 row affected (0.00 sec)mysql> commit;
Query OK, 0 rows affected (0.01 sec)mysql> select * from user;
+----+-----------+-------+
| id | name | money |
+----+-----------+-------+
| 1 | a | 900 |
| 2 | b | 1100 |
| 3 | 小明 | 1000 |
| 4 | 淘宝店 | 1000 |
| 5 | c | 100 |
| 6 | d | 1000 |
+----+-----------+-------+
6 rows in set (0.00 sec)-- 王尼玛-北京
mysql> select * from user;
+----+-----------+-------+
| id | name | money |
+----+-----------+-------+
| 1 | a | 900 |
| 2 | b | 1100 |
| 3 | 小明 | 1000 |
| 4 | 淘宝店 | 1000 |
| 5 | c | 100 |
+----+-----------+-------+
5 rows in set (0.00 sec)mysql> insert into user values(6,'d',1000);
ERROR 1062 (23000): Duplicate entry '6' for key 'PRIMARY'-- 这种现象就叫做幻读！！
-- 事务a 和 事务b 同时操作一张表，事务a提交的数据，也不能被事务b 读到，就可造成幻读。4、serializable; 串行化
-- 修改隔离级别为serializable串行化
set global transaction isolation level serializable;select @@global.transaction_isolation;
+--------------------------------+
| @@global.transaction_isolation |
+--------------------------------+
| SERIALIZABLE |
+--------------------------------+
1 row in set (0.00 sec)mysql> select * from user;
+----+-----------+-------+
| id | name | money |
+----+-----------+-------+
| 1 | a | 900 |
| 2 | b | 1100 |
| 3 | 小明 | 1000 |
| 4 | 淘宝店 | 1000 |
| 5 | c | 100 |
| 6 | d | 1000 |
+----+-----------+-------+
6 rows in set (0.00 sec)
-- 张全蛋-成都
start transaction;insert into user values(7,'赵英俊',1000);mysql> select * from user;
+----+-----------+-------+
| id | name | money |
+----+-----------+-------+
| 1 | a | 900 |
| 2 | b | 1100 |
| 3 | 小明 | 1000 |
| 4 | 淘宝店 | 1000 |
| 5 | c | 100 |
| 6 | d | 1000 |
| 7 | 赵英俊 | 1000 |
+----+-----------+-------+
7 rows in set (0.01 sec)-- 王尼玛-北京
start transaction;
mysql> select * from user;
+----+-----------+-------+
| id | name | money |
+----+-----------+-------+
| 1 | a | 900 |
| 2 | b | 1100 |
| 3 | 小明 | 1000 |
| 4 | 淘宝店 | 1000 |
| 5 | c | 100 |
| 6 | d | 1000 |
| 7 | 赵英俊 | 1000 |
+----+-----------+-------+
7 rows in set (0.01 sec)-- 张全蛋-成都
start transaction;insert into user values(7,'王小花',1000);-- sql语句被卡住了？
insert into user values(8,'王小花',1000);-- 当user 表被另外一个事务操作时，其他事务里面的写操作，是不可以进行的。
-- 进入排队状态（串行化），直到王尼玛那边事务结束之后，张全蛋这个的写入操作才会执行。
--在没有等待超时的情况下。-- 王尼玛-北京
mysql> commit;
Query OK, 0 rows affected (0.00 sec)-- 张全蛋-成都
mysql> insert into user values(8,'王小花',1000);
Query OK, 1 row affected (39.52 sec)-- 串行化的问题是，性能特差！！READ-UNCOMMITTED > READ-COMMITTED > REPEATABLE-READ > SERIALIZABLE
-- 隔离级别越高，性能越差mysql 默认隔离级别是 REPEATABLE-READ一天学会MYSQL数据库_笔记相关推荐
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