数据库
- 常见的数据库
- 查看当前用户及其权限
- 创建用户
- 授权用户访问数据库
- 撤销用户权限
- 修改用户密码
- 删除用户
- 增
- 创建一个数据库
- 创建表
- 表中插入数据
- 表中添加字段（三种方式）
- 删
- 删除表记录
- 删除表字段
- 删除表（三种方式）
- 删除数据库
- 改
- 修改表名
- 修改表数据
- 修改表字段名
- 修改表字段数据类型
- 修改字段排列段顺序
- 查
- 通配符和条件表达式
- order by排序
常见的数据库
当前主流的数据库系统包括关系型数据库管理系统（RDBMS）和一些主要的NoSQL数据库。以下是几个主流的数据库系统：
关系型数据库管理系统 (RDBMS)
MySQL / MariaDB:（本文详细介绍该数据库的命令使用）
MySQL是一个流行的开源关系型数据库管理系统，被广泛应用于Web应用开发中。
MariaDB是MySQL的一个分支，保持与MySQL高度兼容，并添加了一些新的特性。
PostgreSQL:
PostgreSQL是一个强大的开源关系型数据库管理系统，以其功能丰富和可扩展性而闻名。
它支持复杂的查询、事务、触发器等高级数据库特性。
Oracle Database:
Oracle Database是一种商业的关系型数据库管理系统，广泛用于企业级应用。
它以其高可用性、强大的管理功能和丰富的特性集合而著称。
NoSQL非关系型数据库
MongoDB:
MongoDB是一个流行的开源NoSQL数据库，采用文档存储模型，适合处理大量的非结构化数据。
它支持高度灵活的数据模型和分布式部署。
Redis:
Redis是一个开源的内存数据结构存储系统，可以用作数据库、缓存和消息代理。
它支持多种数据结构（如字符串、哈希表、列表等），并提供高性能的读写操作。
ubuntu2404安装mariadb数据库
apt install -y mariadb-server
systemctl enable --now mariadb
查看当前用户及其权限
查看用户语法
SELECT user, host FROM mysql.user;
查看用户权限语法
SHOW GRANTS FOR 'username'@'host';
MariaDB [(none)]> SELECT user, host FROM mysql.user;
+-------------+-----------+
| User | Host |
+-------------+-----------+
| mariadb.sys | localhost |
| mysql | localhost |
| root | localhost |
+-------------+-----------+
4 rows in set (0.001 sec)MariaDB [(none)]> SHOW GRANTS FOR 'mysql'@'localhost';
+------------------------------------------------------------------------------------------------------------------------------------------+
| Grants for mysql@localhost|
+------------------------------------------------------------------------------------------------------------------------------------------+
| GRANT ALL PRIVILEGES ON *.* TO `mysql`@`localhost` IDENTIFIED VIA mysql_native_password USING 'invalid' OR unix_socket WITH GRANT OPTION |
| GRANT PROXY ON ''@'%' TO 'mysql'@'localhost' WITH GRANT OPTION|
+------------------------------------------------------------------------------------------------------------------------------------------+
2 rows in set (0.000 sec)
创建用户
语法格式
CREATE USER 'username'@'host' IDENTIFIED BY 'password';
username: 要创建的用户名。
host: 允许访问数据库的主机名或IP地址。可以使用通配符 % 表示任意主机，或者具体的IP地址或主机名。
password: 用户的密码。
MariaDB [(none)]> CREATE USER 'huhy'@'localhost' IDENTIFIED BY '000000';
Query OK, 0 rows affected (0.001 sec)MariaDB [(none)]> SELECT user, host FROM mysql.user;
+-------------+-----------+
| User | Host |
+-------------+-----------+
| huhy | localhost |
| mariadb.sys | localhost |
| mysql | localhost |
| root | localhost |
+-------------+-----------+
4 rows in set (0.001 sec)
授权用户访问数据库
语法格式
GRANT privileges ON database_name.table_name TO 'username'@'host';
privileges: 用户需要的权限，例如 SELECT, INSERT, UPDATE, DELETE, ALL PRIVILEGES 等。
database_name.table_name: 数据库和表名，可以使用通配符 * 表示所有数据库或表。
username 和 host: 已创建用户的用户名和主机。
例：
GRANT SELECT, INSERT ON database1.* TO 'user1'@'localhost';
GRANT ALL PRIVILEGES ON database2.* TO 'user1'@'%';
GRANT DELETE ON database1.table1 TO 'user1'@'192.168.1.100';
赋予huhy用户所有权限
MariaDB [(none)]> GRANT ALL PRIVILEGES ON *.* TO 'huhy'@'localhost';
Query OK, 0 rows affected (0.001 sec)MariaDB [(none)]> SHOW GRANTS FOR 'huhy'@'localhost';
+----------------------------------------------------------------------------------------------------------------------+
| Grants for huhy@localhost |
+----------------------------------------------------------------------------------------------------------------------+
| GRANT ALL PRIVILEGES ON *.* TO `huhy`@`localhost` IDENTIFIED BY PASSWORD '*032197AE5731D4664921A6CCAC7CFCE6A0698693' |
+----------------------------------------------------------------------------------------------------------------------+
1 row in set (0.000 sec)
撤销用户权限
语法格式
REVOKE privileges ON database_name.table_name FROM 'username'@'host';
撤销huhy所有权限
MariaDB [(none)]> REVOKE ALL PRIVILEGES ON *.* FROM 'huhy'@'localhost';
Query OK, 0 rows affected (0.001 sec)MariaDB [(none)]> SHOW GRANTS FOR 'huhy'@'localhost';
+-------------------------------------------------------------------------------------------------------------+
| Grants for huhy@localhost |
+-------------------------------------------------------------------------------------------------------------+
| GRANT USAGE ON *.* TO `huhy`@`localhost` IDENTIFIED BY PASSWORD '*032197AE5731D4664921A6CCAC7CFCE6A0698693' |
+-------------------------------------------------------------------------------------------------------------+
1 row in set (0.000 sec)MariaDB [(none)]>
如果只需要撤销单个权限；可按照如下
REVOKE SELECT, INSERT ON *.* FROM 'huhy'@'localhost';
修改用户密码
语法格式
ALTER USER 'username'@'host' IDENTIFIED BY 'new_password';
修改用户密码为111111
MariaDB [(none)]> ALTER USER 'huhy'@'localhost' IDENTIFIED BY '111111';
Query OK, 0 rows affected (0.001 sec)
删除用户
语法格式
DROP USER 'username'@'host';
删除huhy
MariaDB [(none)]> drop user 'huhy'@'localhost';
Query OK, 0 rows affected (0.001 sec)MariaDB [(none)]> SELECT user, host FROM mysql.user;
+-------------+-----------+
| User | Host |
+-------------+-----------+
| mariadb.sys | localhost |
| mysql | localhost |
| root | localhost |
+-------------+-----------+
3 rows in set (0.001 sec)MariaDB [(none)]>
以下操作使用mysql数据库
增
创建一个数据库
语法格式
create database 数据库名;
mysql> create database test;
Query OK, 1 row affected (0.00 sec)mysql> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| mysql |
| performance_schema |
| studentdb |
| sys |
| test |
+--------------------+
6 rows in set (0.00 sec)mysql>
创建完后可以用show databases;查看所有数据库，注意databases是复数形式的
创建表
创建表时注意要指定在那个数据库下创建表，用use来选择
创建表语法格式
create table 表名(字段名 数据类型 primary key,字段名 数据类型,字段名 数据类型);
primary key表示该字段不为空且值不能重复
mysql> use test;
Database changed
mysql> create table info(id int primary key,name varchar(255),age varchar(100));
Query OK, 0 rows affected (0.00 sec)mysql> desc info;
+-------+--------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+--------------+------+-----+---------+-------+
| id | int(11) | NO | PRI | NULL | |
| name | varchar(255) | YES | | NULL | |
| age | varchar(100) | YES | | NULL | |
+-------+--------------+------+-----+---------+-------+
3 rows in set (0.00 sec)mysql>
表中插入数据
语法格式
insert into 表名 (字段1,字段2,字段3) values (值1,值2,值3);
mysql> insert into info(id,name,age) values ("1","张三","19");
Query OK, 1 row affected (0.00 sec)mysql> select * from info;
+----+--------+------+
| id | name | age |
+----+--------+------+
| 1 | 张三 | 19 |
+----+--------+------+
1 row in set (0.00 sec)mysql>
这里先提前学习一个查询所有信息命令select * from info
表中添加字段（三种方式）
第一种方式，末尾添加字段
alter table 表名 add 新字段名 数据类型 约束条件(可选);
mysql> desc info;
+-------+--------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+--------------+------+-----+---------+-------+
| id | int(11) | NO | PRI | NULL | |
| name | varchar(255) | YES | | NULL | |
| age | varchar(100) | YES | | NULL | |
+-------+--------------+------+-----+---------+-------+
3 rows in set (0.00 sec)mysql> alter table info add sex varchar(50);
Query OK, 0 rows affected (0.05 sec)
Records: 0 Duplicates: 0 Warnings: 0mysql> desc info;
+-------+--------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+--------------+------+-----+---------+-------+
| id | int(11) | NO | PRI | NULL | |
| name | varchar(255) | YES | | NULL | |
| age | varchar(100) | YES | | NULL | |
| sex | varchar(50) | YES | | NULL | |
+-------+--------------+------+-----+---------+-------+
4 rows in set (0.00 sec)mysql>
第二种方式，开头创建字段
alter table 表名 add 新字段名 数据类型 约束条件(可选) first;
mysql> desc info;
+-------+--------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+--------------+------+-----+---------+-------+
| id | int(11) | NO | PRI | NULL | |
| name | varchar(255) | YES | | NULL | |
| age | varchar(100) | YES | | NULL | |
| sex | varchar(50) | YES | | NULL | |
+-------+--------------+------+-----+---------+-------+
4 rows in set (0.00 sec)mysql> alter table info add num int(10) first;
Query OK, 0 rows affected (0.05 sec)
Records: 0 Duplicates: 0 Warnings: 0mysql> desc info;
+-------+--------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+--------------+------+-----+---------+-------+
| num | int(10) | YES | | NULL | |
| id | int(11) | NO | PRI | NULL | |
| name | varchar(255) | YES | | NULL | |
| age | varchar(100) | YES | | NULL | |
| sex | varchar(50) | YES | | NULL | |
+-------+--------------+------+-----+---------+-------+
5 rows in set (0.00 sec)mysql>
第三种方式，中间添加字段
alter table 表名 add 新字段名 数据类型 约束条件(可选) after 已经存在的字段名;
MySQL 除了允许在表的开头位置和末尾位置添加字段外，还允许在中间位置（指定的字段之后）添加字段，此时需要使用 after 关键字
mysql> desc info;
+-------+--------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+--------------+------+-----+---------+-------+
| num | int(10) | YES | | NULL | |
| id | int(11) | NO | PRI | NULL | |
| name | varchar(255) | YES | | NULL | |
| age | varchar(100) | YES | | NULL | |
| sex | varchar(50) | YES | | NULL | |
+-------+--------------+------+-----+---------+-------+
5 rows in set (0.00 sec)mysql> alter table info add sno varchar(50) after name;
Query OK, 0 rows affected (0.06 sec)
Records: 0 Duplicates: 0 Warnings: 0mysql> desc info;
+-------+--------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+--------------+------+-----+---------+-------+
| num | int(10) | YES | | NULL | |
| id | int(11) | NO | PRI | NULL | |
| name | varchar(255) | YES | | NULL | |
| sno | varchar(50) | YES | | NULL | |
| age | varchar(100) | YES | | NULL | |
| sex | varchar(50) | YES | | NULL | |
+-------+--------------+------+-----+---------+-------+
6 rows in set (0.00 sec)mysql>
删
删除表记录
语法格式如下
delete from 表名 where 字段 = 值;
注；如果不加上where条件语句的话，就会把整张表给删除了
mysql> delete from info where id = 1;
Query OK, 1 row affected (0.00 sec)mysql> select * from info;
Empty set (0.00 sec)mysql>
删除表字段
命令格式
alter table 表名 drop column 字段名;
mysql> desc info;
+-------+--------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+--------------+------+-----+---------+-------+
| id | int(11) | NO | PRI | NULL | |
| name | varchar(255) | YES | | NULL | |
| age | varchar(100) | YES | | NULL | |
+-------+--------------+------+-----+---------+-------+
3 rows in set (0.00 sec)mysql> alter table info drop column age;
Query OK, 0 rows affected (0.05 sec)
Records: 0 Duplicates: 0 Warnings: 0mysql> desc info;
+-------+--------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+--------------+------+-----+---------+-------+
| id | int(11) | NO | PRI | NULL | |
| name | varchar(255) | YES | | NULL | |
+-------+--------------+------+-----+---------+-------+
2 rows in set (0.00 sec)mysql>
删除表（三种方式）
第一种方式；
drop table 表名;
删除内容和定义，删除的是整个表（结构和数据），将表所占用的空间全释放掉。无法回滚，所以删除是不能恢复的，如果再次使用的话需要新建表
mysql> show tables;
+----------------+
| Tables_in_test |
+----------------+
| info |
+----------------+
1 row in set (0.00 sec)mysql> select * from info;
+----+--------+------+
| id | name | age |
+----+--------+------+
| 1 | 张三 | 19 |
+----+--------+------+
1 row in set (0.00 sec)mysql> drop table info;
Query OK, 0 rows affected (0.01 sec)mysql> show tables;
Empty set (0.00 sec)mysql>
第二种删除方式
truncate table 表名;
只是清空表，删除内容，释放空间，但不删除定义（保留表的数据结构）。且不会把删除操作记录记入日志保存，无法回滚，所以删除是不能恢复的。并且在删除的过程中不会激活与表有关的删除触发器。执行速度快。
mysql> show tables;
+----------------+
| Tables_in_test |
+----------------+
| info |
+----------------+
1 row in set (0.00 sec)mysql> select * from info;
+----+--------+------+
| id | name | age |
+----+--------+------+
| 1 | 张三 | 19 |
+----+--------+------+
1 row in set (0.00 sec)mysql> truncate table info;
Query OK, 0 rows affected (0.01 sec)mysql> show tables;
+----------------+
| Tables_in_test |
+----------------+
| info |
+----------------+
1 row in set (0.00 sec)mysql> select * from info;
Empty set (0.00 sec)mysql>
第三中删除方式
delete from 表名;
删除表中的行，不删除表的结构。执行删除的过程是每次从表中删除一行，并且将该行的删除操作作为事务在日志中保存，以便进行进行回滚操作。delete会根据指定的条件删除表中满足条件的数据，where就是条件判断。如果不指定where子句，那么删除表中所有记录。delete操作不会减少表或索引所占用的空间,不推荐此方法删除表
删除数据库
语法格式
drop database 数据库名;
数据库删除之后，原来分配的空间将被收回。需要注意的是，数据库删除之后该数据库中所有的表和数据都将被删除。因此删除数据库要特别小心
mysql> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| mysql |
| performance_schema |
| studentdb |
| sys |
| test |
+--------------------+
6 rows in set (0.00 sec)mysql> drop database test;
Query OK, 1 row affected (0.01 sec)mysql> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| mysql |
| performance_schema |
| studentdb |
| sys |
+--------------------+
5 rows in set (0.00 sec)mysql>
改
修改表名
语法格式
alter table 旧表名 rename 新表名;
mysql> show tables;
+----------------+
| Tables_in_test |
+----------------+
| info |
+----------------+
1 row in set (0.00 sec)mysql> alter table info rename new_info;
Query OK, 0 rows affected (0.00 sec)mysql> show tables;
+----------------+
| Tables_in_test |
+----------------+
| new_info |
+----------------+
1 row in set (0.00 sec)mysql>
修改表数据
语法格式
update 表名 set 字段名 = ”新的值“ where 条件;
注意判断的条件是否锁定为修改修改的字段
mysql> select * from info;
+------+----+--------+------+------+------+
| num | id | name | sno | age | sex |
+------+----+--------+------+------+------+
| NULL | 1 | 张三 | NULL | 19 | NULL |
+------+----+--------+------+------+------+
1 row in set (0.00 sec)mysql> update info set sex = "男" where id = 1;
Query OK, 1 row affected (0.00 sec)
Rows matched: 1 Changed: 1 Warnings: 0mysql> select * from info;
+------+----+--------+------+------+------+
| num | id | name | sno | age | sex |
+------+----+--------+------+------+------+
| NULL | 1 | 张三 | NULL | 19 | 男 |
+------+----+--------+------+------+------+
1 row in set (0.00 sec)mysql>
修改表字段名
语法格式
alter table 表名 change 字段名 旧字段 新字段 新字段数据类型;
注；此方式可以修改字段名字的同时也可以修改字段数据类型，也可以指定为原来的字段类型
mysql> desc info;
+-------+--------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+--------------+------+-----+---------+-------+
| num | int(10) | YES | | NULL | |
| id | int(11) | NO | PRI | NULL | |
| name | varchar(255) | YES | | NULL | |
| sno | varchar(50) | YES | | NULL | |
| age | varchar(100) | YES | | NULL | |
| sex | varchar(50) | YES | | NULL | |
+-------+--------------+------+-----+---------+-------+
6 rows in set (0.00 sec)mysql> alter table info change name new_name varchar(100);
Query OK, 1 row affected (0.01 sec)
Records: 1 Duplicates: 0 Warnings: 0mysql> desc info;
+----------+--------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+----------+--------------+------+-----+---------+-------+
| num | int(10) | YES | | NULL | |
| id | int(11) | NO | PRI | NULL | |
| new_name | varchar(100) | YES | | NULL | |
| sno | varchar(50) | YES | | NULL | |
| age | varchar(100) | YES | | NULL | |
| sex | varchar(50) | YES | | NULL | |
+----------+--------------+------+-----+---------+-------+
6 rows in set (0.00 sec)mysql>
修改表字段数据类型
语法格式
alter table 表名 modify 字段名 数据类型(长度);
mysql> desc info;
+----------+--------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+----------+--------------+------+-----+---------+-------+
| num | int(10) | YES | | NULL | |
| id | int(11) | NO | PRI | NULL | |
| new_name | varchar(100) | YES | | NULL | |
| sno | varchar(50) | YES | | NULL | |
| age | varchar(100) | YES | | NULL | |
| sex | varchar(50) | YES | | NULL | |
+----------+--------------+------+-----+---------+-------+
6 rows in set (0.00 sec)mysql> alter table info modify age varchar(10);
Query OK, 1 row affected (0.01 sec)
Records: 1 Duplicates: 0 Warnings: 0mysql> desc info;
+----------+--------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+----------+--------------+------+-----+---------+-------+
| num | int(10) | YES | | NULL | |
| id | int(11) | NO | PRI | NULL | |
| new_name | varchar(100) | YES | | NULL | |
| sno | varchar(50) | YES | | NULL | |
| age | varchar(10) | YES | | NULL | |
| sex | varchar(50) | YES | | NULL | |
+----------+--------------+------+-----+---------+-------+
6 rows in set (0.00 sec)mysql>
修改字段排列段顺序
方式一，将指定字段放在开头
alter table 表名 modify 字段名 字段类型 first;
mysql> desc info;
+----------+--------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+----------+--------------+------+-----+---------+-------+
| num | int(10) | YES | | NULL | |
| id | int(11) | NO | PRI | NULL | |
| new_name | varchar(100) | YES | | NULL | |
| sno | varchar(50) | YES | | NULL | |
| age | varchar(10) | YES | | NULL | |
| sex | varchar(50) | YES | | NULL | |
+----------+--------------+------+-----+---------+-------+
6 rows in set (0.00 sec)mysql> alter table info modify id int(11) first;
Query OK, 0 rows affected (0.06 sec)
Records: 0 Duplicates: 0 Warnings: 0mysql> desc info;
+----------+--------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+----------+--------------+------+-----+---------+-------+
| id | int(11) | NO | PRI | NULL | |
| num | int(10) | YES | | NULL | |
| new_name | varchar(100) | YES | | NULL | |
| sno | varchar(50) | YES | | NULL | |
| age | varchar(10) | YES | | NULL | |
| sex | varchar(50) | YES | | NULL | |
+----------+--------------+------+-----+---------+-------+
6 rows in set (0.00 sec)mysql>
第二种方式，指定为某字段的后面
alter table 表名 modify 字段名 字段类型 after 字段名;
mysql> desc info;
+----------+--------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+----------+--------------+------+-----+---------+-------+
| id | int(11) | NO | PRI | NULL | |
| num | int(10) | YES | | NULL | |
| new_name | varchar(100) | YES | | NULL | |
| sno | varchar(50) | YES | | NULL | |
| age | varchar(10) | YES | | NULL | |
| sex | varchar(50) | YES | | NULL | |
+----------+--------------+------+-----+---------+-------+
6 rows in set (0.00 sec)mysql> alter table info modify num int(10) after sex;
Query OK, 0 rows affected (0.03 sec)
Records: 0 Duplicates: 0 Warnings: 0mysql> desc info;
+----------+--------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+----------+--------------+------+-----+---------+-------+
| id | int(11) | NO | PRI | NULL | |
| new_name | varchar(100) | YES | | NULL | |
| sno | varchar(50) | YES | | NULL | |
| age | varchar(10) | YES | | NULL | |
| sex | varchar(50) | YES | | NULL | |
| num | int(10) | YES | | NULL | |
+----------+--------------+------+-----+---------+-------+
6 rows in set (0.00 sec)mysql>
拓展；如果字段的数据类型写错了也是会被修改的，并且还是会排序在指定字段的后面
mysql> desc info;
+----------+--------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+----------+--------------+------+-----+---------+-------+
| id | int(11) | NO | PRI | NULL | |
| new_name | varchar(100) | YES | | NULL | |
| sno | varchar(50) | YES | | NULL | |
| age | varchar(10) | YES | | NULL | |
| sex | varchar(50) | YES | | NULL | |
| num | int(10) | YES | | NULL | |
+----------+--------------+------+-----+---------+-------+
6 rows in set (0.00 sec)mysql> alter table info modify num int(100) after sex;
Query OK, 0 rows affected (0.00 sec)
Records: 0 Duplicates: 0 Warnings: 0mysql> desc info;
+----------+--------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+----------+--------------+------+-----+---------+-------+
| id | int(11) | NO | PRI | NULL | |
| new_name | varchar(100) | YES | | NULL | |
| sno | varchar(50) | YES | | NULL | |
| age | varchar(10) | YES | | NULL | |
| sex | varchar(50) | YES | | NULL | |
| num | int(100) | YES | | NULL | |
+----------+--------------+------+-----+---------+-------+
6 rows in set (0.00 sec)查
通配符和条件表达式
可参考菜鸟教程
order by排序
升序
select 字段1,字段2 from 表名 order by 排序字段 desc;
mysql> select * from student;
+-----------+-----------+------+------+-------+------+
| sno | sname | ssex | sage | sdept | sloc |
+-----------+-----------+------+------+-------+------+
| 201215121 | 李勇 | 男 | 22 | cs | NULL |
| 201215122 | 刘晨 | 女 | 20 | cs | NULL |
| 201215123 | 王敏 | 女 | 18 | ma | NULL |
| 201215124 | 张月琳 | 女 | 20 | cs | NULL |
| 201215125 | 张立 | 男 | 19 | is | NULL |
| 201215126 | 李晚 | 男 | 21 | is | NULL |
| 201215127 | 林方成 | 男 | 19 | cs | NULL |
| 201215128 | 赵立何 | 男 | 21 | ma | NULL |
| 201215129 | 赵城 | 男 | 20 | ma | NULL |
| 201215130 | 张浩 | 男 | 20 | is | NULL |
| 201215131 | 王信韵 | 女 | 19 | cs | NULL |
| 201215132 | 孙思 | 女 | 21 | ma | NULL |
| 201215133 | 陈信 | 女 | 22 | cs | NULL |
+-----------+-----------+------+------+-------+------+
13 rows in set (0.00 sec)mysql> select sno,sname from student order by sno desc;
+-----------+-----------+
| sno | sname |
+-----------+-----------+
| 201215133 | 陈信 |
| 201215132 | 孙思 |
| 201215131 | 王信韵 |
| 201215130 | 张浩 |
| 201215129 | 赵城 |
| 201215128 | 赵立何 |
| 201215127 | 林方成 |
| 201215126 | 李晚 |
| 201215125 | 张立 |
| 201215124 | 张月琳 |
| 201215123 | 王敏 |
| 201215122 | 刘晨 |
| 201215121 | 李勇 |
+-----------+-----------+
13 rows in set (0.00 sec)mysql>
降序
select 字段1,字段2 from 表名 order by 排序字段 asc;
mysql> select * from student;
+-----------+-----------+------+------+-------+------+
| sno | sname | ssex | sage | sdept | sloc |
+-----------+-----------+------+------+-------+------+
| 201215121 | 李勇 | 男 | 22 | cs | NULL |
| 201215122 | 刘晨 | 女 | 20 | cs | NULL |
| 201215123 | 王敏 | 女 | 18 | ma | NULL |
| 201215124 | 张月琳 | 女 | 20 | cs | NULL |
| 201215125 | 张立 | 男 | 19 | is | NULL |
| 201215126 | 李晚 | 男 | 21 | is | NULL |
| 201215127 | 林方成 | 男 | 19 | cs | NULL |
| 201215128 | 赵立何 | 男 | 21 | ma | NULL |
| 201215129 | 赵城 | 男 | 20 | ma | NULL |
| 201215130 | 张浩 | 男 | 20 | is | NULL |
| 201215131 | 王信韵 | 女 | 19 | cs | NULL |
| 201215132 | 孙思 | 女 | 21 | ma | NULL |
| 201215133 | 陈信 | 女 | 22 | cs | NULL |
+-----------+-----------+------+------+-------+------+
13 rows in set (0.00 sec)mysql> select sno,sname from student order by sno asc;
+-----------+-----------+
| sno | sname |
+-----------+-----------+
| 201215121 | 李勇 |
| 201215122 | 刘晨 |
| 201215123 | 王敏 |
| 201215124 | 张月琳 |
| 201215125 | 张立 |
| 201215126 | 李晚 |
| 201215127 | 林方成 |
| 201215128 | 赵立何 |
| 201215129 | 赵城 |
| 201215130 | 张浩 |
| 201215131 | 王信韵 |
| 201215132 | 孙思 |
| 201215133 | 陈信 |
+-----------+-----------+
13 rows in set (0.00 sec)mysql>
)
