MySQL高级语法

视图

作用：将查询语句封装成一张可视化的表，封装的是动态SQL语句，会根据数据表的数据而更新

创建视图

• 语法：create view 视图名 as 查询语句;

（1）准备数据

MariaDB [db1]> create table ping (
    -> id int primary key,
    -> name varchar(20)
    -> );
Query OK, 0 rows affected (0.008 sec)

MariaDB [db1]> insert into ping values(1,'sunyingsha'),(2,'ch;enmeng'),(3,'wangmanyu');
Query OK, 3 rows affected (0.003 sec)
Records: 3  Duplicates: 0  Warnings: 0

MariaDB [db1]> select * from ping;
+----+------------+
| id | name       |
+----+------------+
|  1 | sunyingsha |
|  2 | ch;enmeng  |
|  3 | wangmanyu  |
+----+------------+
3 rows in set (0.001 sec)

（2）创建视图

MariaDB [db1]> create view get_ping as select * from ping order by id desc;
Query OK, 0 rows affected (0.003 sec)

查看视图

MariaDB [db1]> show tables;
+---------------+
| Tables_in_db1 |
+---------------+
| get_ping      |
| ping          |
| xinxi         |
+---------------+
3 rows in set (0.000 sec)

查看视图结果

MariaDB [db1]> select * from get_ping;
+----+------------+
| id | name       |
+----+------------+
|  3 | wangmanyu  |
|  2 | ch;enmeng  |
|  1 | sunyingsha |
+----+------------+
3 rows in set (0.001 sec)

查看视图创建语句

MariaDB [db1]> show create view get_ping;
+----------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------+----------------------+
| View     | Create View                                                                                                                                                                            | character_set_client | collation_connection |
+----------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------+----------------------+
| get_ping | CREATE ALGORITHM=UNDEFINED DEFINER=`root`@`localhost` SQL SECURITY DEFINER VIEW `get_ping` AS select `ping`.`id` AS `id`,`ping`.`name` AS `name` from `ping` order by `ping`.`id` desc | utf8                 | utf8_general_ci      |
+----------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------+----------------------+
1 row in set (0.001 sec)

修改视图

MariaDB [db1]> alter view get_ping as select id from ping;
Query OK, 0 rows affected (0.003 sec)

MariaDB [db1]> select * from get_ping;
+----+
| id |
+----+
|  1 |
|  2 |
|  3 |
+----+
3 rows in set (0.001 sec)

删除视图

MariaDB [db1]> drop view get_ping;
Query OK, 0 rows affected (0.000 sec)

多表关联

• 语法：select * from 主表名 inner|left|right join 副表名 on 主表.字段=副表.字段;
• inner join：两边都有记录
• left join：以主表记录为主
• right join：以副表记录为主
• 查询过程中的执行顺序：from>where>group（包含聚合函数，如min、max、avg等）>having>order>select外键

调用函数

• count：统计
• distinct：去重
• avg：获取平均值
• min/max：最小值/最大值
• sum：求和
• year/month/day：获取年/月/日的部分

准备两张数据表

mysql> create database db2;
mysql> use db2
mysql> create table xinxi(
id int auto_increment,
name varchar(20) not null,
sex int(1) not null default 0,
birth datetime,
primary key(id)
);
mysql> alter table xinxi add unique key(name);
mysql> insert into xinxi(name,sex,birth) values('xiaozhan',0,'1990-1-1'),
('luhan',0,'1990-4-20'),('liying',1,'1988-1-1'),('baby',1,'1989-1-1');
mysql> create table paihangbang(
id int not null,
score int,
rank int,
name varchar(20)
);
mysql> insert into paihangbang values(1,100,1,'xiaozhan'),(2,98,2,'luhan'),
(3,97,3,'tangyan'),(4,96,4,'liying');

连接两张数据表

MariaDB [db2]> select * from xinxi inner join paihangbang on
    -> xinxi.name=paihangbang.name;
+----+----------+-----+---------------------+----+-------+------+----------+
| id | name     | sex | birth               | id | score | rank | name     |
+----+----------+-----+---------------------+----+-------+------+----------+
|  1 | xiaozhan |   0 | 1990-01-01 00:00:00 |  1 |   100 |    1 | xiaozhan |
|  2 | luhan    |   0 | 1990-04-20 00:00:00 |  2 |    98 |    2 | luhan    |
|  3 | liying   |   1 | 1988-01-01 00:00:00 |  4 |    96 |    4 | liying   |
+----+----------+-----+---------------------+----+-------+------+----------+
3 rows in set (0.001 sec)

MariaDB [db2]> select * from xinxi left join paihangbang on xinxi.name=paihangbang.name;
+----+----------+-----+---------------------+------+-------+------+----------+
| id | name     | sex | birth               | id   | score | rank | name     |
+----+----------+-----+---------------------+------+-------+------+----------+
|  1 | xiaozhan |   0 | 1990-01-01 00:00:00 |    1 |   100 |    1 | xiaozhan |
|  2 | luhan    |   0 | 1990-04-20 00:00:00 |    2 |    98 |    2 | luhan    |
|  3 | liying   |   1 | 1988-01-01 00:00:00 |    4 |    96 |    4 | liying   |
|  4 | baby     |   1 | 1989-01-01 00:00:00 | NULL |  NULL | NULL | NULL     |
+----+----------+-----+---------------------+------+-------+------+----------+
4 rows in set (0.001 sec)

MariaDB [db2]> select * from xinxi right join paihangbang on
    -> xinxi.name=paihangbang.name;
+------+----------+------+---------------------+----+-------+------+----------+
| id   | name     | sex  | birth               | id | score | rank | name     |
+------+----------+------+---------------------+----+-------+------+----------+
|    1 | xiaozhan |    0 | 1990-01-01 00:00:00 |  1 |   100 |    1 | xiaozhan |
|    2 | luhan    |    0 | 1990-04-20 00:00:00 |  2 |    98 |    2 | luhan    |
| NULL | NULL     | NULL | NULL                |  3 |    97 |    3 | tangyan  |
|    3 | liying   |    1 | 1988-01-01 00:00:00 |  4 |    96 |    4 | liying   |
+------+----------+------+---------------------+----+-------+------+----------+
4 rows in set (0.000 sec)

多表联查

准备数据

#创建数据库:mysql_test
mysql> drop database if exists mysql_test;
mysql> create database mysql_test;
mysql> use mysql_test;
#创建学生表:student
mysql> create table student (
s_id int,
s_name varchar(8),
s_birth date,
s_sex varchar(4)
) default charset utf8;
#插入数据
mysql> insert into student values
(1,'赵雷','1990-01-01','男'),(2,'钱电','1990-12-21','男'),(3,'孙风','1990-05-20','男'),
(4,'李云','1990-08-06','男'),(5,'周梅','1991-12-01','女'),(6,'吴兰','1992-03-01','女'),
(7,'郑竹','1989-07-01','女'),(8,'王菊','1990-01-20','女');
#创建课程表：course
mysql> create table course (
c_id int,
c_name varchar(8),
t_id int
)default charset utf8;
#插入数据
mysql> insert into course values(1,'语文',2),(2,'数学',1),(3,'英语',3);
#创建成绩表score
mysql> create table score (
s_id int,
c_id int,
s_score int
)default charset utf8;
#插入数据
mysql> insert into score values(1,1,80),(1,2,90),(1,3,99),(2,1,70),(2,2,60),
(2,3,65),(3,1,80),(3,2,80),(3,3,80),(4,1,50),(4,2,30),(4,3,40),(5,1,76),
(5,2,87),(6,1,31),(6,3,34),(7,2,89),(7,3,98);

查询需求

（1）查询"李"姓学生的数量

MariaDB [mysql_test]> select count(*) as cnt_name_li from student where s_name like '李%';
+-------------+
| cnt_name_li |
+-------------+
|           1 |
+-------------+
1 row in set (0.001 sec)

（2）查询"01"课程的学生的信息及课程分数

MariaDB [mysql_test]> select s.*,score.s_score from student s inner join score on s.s_id = score.s_id;
+------+--------+------------+-------+---------+
| s_id | s_name | s_birth    | s_sex | s_score |
+------+--------+------------+-------+---------+
|    1 | 赵雷   | 1990-01-01 | 男    |      80 |
|    1 | 赵雷   | 1990-01-01 | 男    |      90 |
|    1 | 赵雷   | 1990-01-01 | 男    |      99 |
|    2 | 钱电   | 1990-12-21 | 男    |      70 |
|    2 | 钱电   | 1990-12-21 | 男    |      60 |
|    2 | 钱电   | 1990-12-21 | 男    |      65 |
|    3 | 孙风   | 1990-05-20 | 男    |      80 |
|    3 | 孙风   | 1990-05-20 | 男    |      80 |
|    3 | 孙风   | 1990-05-20 | 男    |      80 |
|    4 | 李云   | 1990-08-06 | 男    |      50 |
|    4 | 李云   | 1990-08-06 | 男    |      30 |
|    4 | 李云   | 1990-08-06 | 男    |      40 |
|    5 | 周梅   | 1991-12-01 | 女    |      76 |
|    5 | 周梅   | 1991-12-01 | 女    |      87 |
|    6 | 吴兰   | 1992-03-01 | 女    |      31 |
|    6 | 吴兰   | 1992-03-01 | 女    |      34 |
|    7 | 郑竹   | 1989-07-01 | 女    |      89 |
|    7 | 郑竹   | 1989-07-01 | 女    |      98 |
+------+--------+------------+-------+---------+
18 rows in set (0.001 sec)

（3）查询"01"课程比"02"课程成绩高的学生的信息及课程分数

MariaDB [mysql_test]> select s.*,sc1.s_score as score_01,sc2.s_score as score_02
    -> from student s
    -> inner join (
    -> select * from score where c_id = 1
    -> ) sc1
    -> on s.s_id = sc1.s_id
    -> inner join (
    -> select * from score where c_id = 2
    -> ) sc2
    -> on s.s_id = sc2.s_id
    -> where sc1.s_score > sc2.s_score;
+------+--------+------------+-------+----------+----------+
| s_id | s_name | s_birth    | s_sex | score_01 | score_02 |
+------+--------+------------+-------+----------+----------+
|    2 | 钱电   | 1990-12-21 | 男    |       70 |       60 |
|    4 | 李云   | 1990-08-06 | 男    |       50 |       30 |
+------+--------+------------+-------+----------+----------+
2 rows in set (0.002 sec)

支持中文

方法一：建表时支持中文

MariaDB [db2]> create table tzhong(
    -> id int,
    -> name varchar(20),
    -> sex int)DEFAULT CHARSET=utf8 collate=utf8_general_ci;
Query OK, 0 rows affected (0.008 sec)

测试：

MariaDB [db2]> insert into tzhong values(1,'哈哈哈',0);
Query OK, 1 row affected (0.001 sec)

MariaDB [db2]> select * from tzhong;
+------+-----------+------+
| id   | name      | sex  |
+------+-----------+------+
|    1 | 哈哈哈    |    0 |
+------+-----------+------+
1 row in set (0.001 sec)

方法二：建库时支持中文

MariaDB [db2]> create database db10 DEFAULT CHARSET=utf8 collate=utf8_general_ci;
Query OK, 1 row affected (0.001 sec)

测试：

MariaDB [db10]> create table tzhong(
    -> id int,
    -> name varchar(20),
    -> sex int);
Query OK, 0 rows affected (0.006 sec)

MariaDB [db10]> show create table tzhong;
+--------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Table  | Create Table                                                                                                                                                                      |
+--------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| tzhong | CREATE TABLE `tzhong` (
  `id` int(11) DEFAULT NULL,
  `name` varchar(20) DEFAULT NULL,
  `sex` int(11) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_general_ci |
+--------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.001 sec)

方法三：修改服务配置文件

[root@localhost ~]# vim /etc/my.cnf.d/mariadb-server.cnf 
[mysqld]

character-set-server=utf8

重启服务，测试：

MariaDB [(none)]> create database 新库;
Query OK, 1 row affected (0.001 sec)

MariaDB [(none)]> show databases;
+--------------------+
| Database           |
+--------------------+
| db1                |
| db10               |
| db2                |
| information_schema |
| mysql              |
| performance_schema |
| 新库               |
+--------------------+
7 rows in set (0.001 sec)

表间约束：外键

特点：

• 外键约束，参照完整性，用来在两个表的数据之间建立连接；
• 一张表可以设置多个外键，一个外键可以加载单列或多列上；
• 外键是表中的一个字段、不一定是本表的主键，但需要对应另一个表的唯一键；
• 关联的两张表的字段类型、字符集需要相同；

语法：

• ALTER TABLE <数据表名> ADD CONSTRAINT <索引名> FOREIGN KEY(<列名>) REFERENCES <主表名> (<列名>);

创建外键

MariaDB [db2]> alter table paihangbang add constraint fk_name foreign key(name) references xinxi(name);
Query OK, 3 rows affected (0.018 sec)              
Records: 3  Duplicates: 0  Warnings: 0

• constraint：级联关系
• 想删除主表的字段，需要把该字段上关联的外键先删除
• 想添加从表的字段，需要在主表的数据范围里面

注：如果paihangbang表中的数据不在xinxi这张表的范围内，则外键会创建失败

查看外键

MariaDB [db2]> show create table paihangbang;
+-------------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Table       | Create Table                                                                                                                                                                                                                                                                                                               |
+-------------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| paihangbang | CREATE TABLE `paihangbang` (
  `id` int(11) NOT NULL,
  `score` int(11) DEFAULT NULL,
  `rank` int(11) DEFAULT NULL,
  `name` varchar(20) DEFAULT NULL,
  KEY `fk_name` (`name`),
  CONSTRAINT `fk_name` FOREIGN KEY (`name`) REFERENCES `xinxi` (`name`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1 COLLATE=latin1_swedish_ci |
+-------------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.000 sec)

删除外键

• 语法：ALTER TABLE <表名> DROP FOREIGN KEY <外键约束名>; #删约束

• 语法：drop index 约束名 on 表名; #删外键索引

  #删除级联
  MariaDB [db2]> alter table paihangbang drop foreign key fk_name;
  Query OK, 0 rows affected (0.003 sec)
  Records: 0 Duplicates: 0 Warnings: 0
  #再删索引
  MariaDB [db2]> drop index fk_name on paihangbang;
  Query OK, 0 rows affected (0.004 sec)
  Records: 0 Duplicates: 0 Warnings: 0

存储过程

• 存储过程(stored procedure)：是将一组SQL语句作为一个整体来执行的数据库对象，通过被调用来运行；
• 和函数一样，是一条或多条SQL语句的集合，区别函数是已经定义好的、存储过程是用户自己定义的；

调用函数

MariaDB [db2]> select * from paihangbang;
+----+-------+------+----------+
| id | score | rank | name     |
+----+-------+------+----------+
|  1 |   100 |    1 | xiaozhan |
|  2 |    98 |    2 | luhan    |
|  4 |    96 |    4 | liying   |
+----+-------+------+----------+
3 rows in set (0.000 sec)
#调用sum函数求和
MariaDB [db2]> select sum(score) as 总分 from paihangbang;
+--------+
| 总分   |
+--------+
|    294 |
+--------+
1 row in set (0.001 sec)
#调用avg函数求平均值
MariaDB [db2]> select avg(score) as 总分 from paihangbang;
+---------+
| 总分    |
+---------+
| 98.0000 |
+---------+
1 row in set (0.001 sec)

MariaDB [mysql_test]> select s_id from score;
+------+
| s_id |
+------+
|    1 |
|    1 |
|    1 |
|    2 |
|    2 |
|    2 |
|    3 |
|    3 |
|    3 |
|    4 |
|    4 |
|    4 |
|    5 |
|    5 |
|    6 |
|    6 |
|    7 |
|    7 |
+------+
18 rows in set (0.000 sec)
#查询结果去重------distinct
MariaDB [mysql_test]> select distinct s_id from score;
+------+
| s_id |
+------+
|    1 |
|    2 |
|    3 |
|    4 |
|    5 |
|    6 |
|    7 |
+------+
7 rows in set (0.000 sec)

定义存储过程

mysql> create procedure delete_data()
#存储过程开始
begin
    #要执行的语句1
    delete from paihangbang where id=2; -对，执行
    #要执行的语句2
    delete from xinxi2 where id=2; -若错，终止
    #存储过程结束
end

注：语句之间单独执行，除非加事务

调用存储过程

• mysql> call delete_data;

支持事务ACDI

过程：开启事务------操作------成功：commit提交事务|失败：rollback回滚

• A：原子性，事务里的语句要么全部执行、要么全部不执行
• C：一致性，事务运行时不改变数据库中的数据
• I：隔离性，指两个以上事务间独立运行、互不干扰
• D：持久性，事务运行完对文件影响是持久的、不会随意回滚

定义带事务的存储过程

mysql> CREATE PROCEDURE delete_data_with_rollback()
#存储过程开始
begin
    #定义错误变量t_error，默认值为0
    declare t_error int;
    #定义检查到语句错误，将t_error的值改为1
    declare continue handler for sqlexception set t_error=1;
    #开启事务
    start transaction;
        #先删paihangbang数据
        delete from paihangbang;
        #再删xinxi数据，故意写错了表名（xinxi - xinxix）
        delete from xinxi;
        #使用if结构，若t_error的值是1则rollback，否则commit
        #rollback或commit都会结束事务
        if t_error =1 then
            rollback;
        else
            commit;
        end if;
    #存储过程结束
    end

注：运行上述步骤之后，表中的数据并不会消失，因为事务还没有真正执行并提交

#执行事务
MariaDB [db2]> call delete_data_with_rollback;
Query OK, 6 rows affected (0.002 sec)

MariaDB [db2]> select * from xinxi;
Empty set (0.001 sec)
#表中数据被清除

查看存储过程

• mysql> show create procedure delete_data;

  #查看所有存储过程
  MariaDB [db2]> show procedure status;
  +-------+---------------------------+-----------+-----------------------+---------------------+---------------------+---------------+---------+----------------------+----------------------+--------------------+
  | Db | Name | Type | Definer | Modified | Created | Security_type | Comment | character_set_client | collation_connection | Database Collation |
  +-------+---------------------------+-----------+-----------------------+---------------------+---------------------+---------------+---------+----------------------+----------------------+--------------------+
  | db2 | delete_data_with_rollback | PROCEDURE | lisi@% | 2025-09-19 18:13:06 | 2025-09-19 18:13:06 | DEFINER | | utf8 | utf8_general_ci | latin1_swedish_ci |
  | mysql | AddGeometryColumn | PROCEDURE | mariadb.sys@localhost | 2025-09-16 21:09:14 | 2025-09-16 21:09:14 | INVOKER | | utf8 | utf8_general_ci | latin1_swedish_ci |
  | mysql | DropGeometryColumn | PROCEDURE | mariadb.sys@localhost | 2025-09-16 21:09:14 | 2025-09-16 21:09:14 | INVOKER | | utf8 | utf8_general_ci | latin1_swedish_ci |
  +-------+---------------------------+-----------+-----------------------+---------------------+---------------------+---------------+---------+----------------------+----------------------+--------------------+
  3 rows in set (0.002 sec)

  #查看存储过程内容
  MariaDB [db2]> show create procedure delete_data_with_rollback;
  +---------------------------+-------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------+----------------------+--------------------+
  | Procedure | sql_mode | Create Procedure | character_set_client | collation_connection | Database Collation |
  +---------------------------+-------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------+----------------------+--------------------+
  | delete_data_with_rollback | STRICT_TRANS_TABLES,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION | CREATE DEFINER=lisi@% PROCEDURE delete_data_with_rollback()
  begin
  declare t_error int;
  declare continue handler for sqlexception set t_error=1;
  start transaction;
  delete from paihangbang;
  delete from xinxix;
  if t_error =1 then
  rollback;
  else
  commit;
  end if;
  end | utf8 | utf8_general_ci | latin1_swedish_ci |
  +---------------------------+-------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------+----------------------+--------------------+
  1 row in set (0.001 sec)

删除存储过程

• mysql> drop procedure delete_data;

  MariaDB [db2]> drop procedure delete_data_with_rollback;
  Query OK, 0 rows affected (0.003 sec)

  MariaDB [db2]> drop procedure delete_data_with_rollback;
  ERROR 1305 (42000): PROCEDURE db2.delete_data_with_rollback does not exist

事务的隔离级别

1. READ_UNCOMMITTED（读未提交）------读脏数据
2. READ_COMMITTED（读已提交）------不可重复读
3. REPEATABLE_READ（可重复读，MySQL默认）
4. SERIALIZABLE（串行读）

查看mysql的隔离级别

• mysql> show variables like 'tx_isolation';

• 或：

• mysql> select @@tx_isolation;

  MariaDB [db2]> show variables like 'tx_isolation';
  +---------------+-----------------+
  | Variable_name | Value |
  +---------------+-----------------+
  | tx_isolation | REPEATABLE-READ |
  +---------------+-----------------+
  1 row in set (0.001 sec)

修改默认存储引擎

vim /etc/my.cnf.d/mariadb-server.cnf

[mysqld]
default-storage-engine=INNODB

systemctl restart mariadb