1、CMD打开执行命令：mysql -u root -p 输入数据库密码，进入数据库
PS C:\Users\admin> mysql -u root -p
Enter password: ****
Welcome to the MariaDB monitor. Commands end with ; or \g.
Your MariaDB connection id is 11
Server version: 10.4.7-MariaDB mariadb.org binary distribution
Copyright (c) 2000, 2018, Oracle, MariaDB Corporation Ab and others.
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
2、执行show databases; ,查看MariaDB的数据库结构。
MariaDB [(none)]> show databases;
+--------------------+
| Database |
+--------------------+
| django |
| information_schema |
| mysql |
| performance_schema |
| test |
+--------------------+
5 rows in set (0.000 sec)
3、新建一个库，名字叫my。
MariaDB [test]> create database my;
Database changed
4、可以再次通过show databases查看新建的库5、使用库：use my6、新建一个表单：sql语句如下
MariaDB [my]> create table my.student(
-> id int(4) primary key,
-> name varchar(4) not null,
-> age int(2) not null
-> );
注：语句的结构如果错误，就会出现问题。错一点点都不行，反例如下：
MariaDB [my]> create table my.student(
-> id int(4) primary key,
-> name varchar(4) not null,
-> age int(2) not null, #此处多了一个,导致了报错
-> );
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near ')' at line 5
7、查看表情况
MariaDB [my]> show tables;
+--------------+
| Tables_in_my |
+--------------+
| student |
+--------------+
1 row in set (0.000 sec)
8、查看表的字段信息
MariaDB [my]> desc student
-> ;
+-------+------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+------------+------+-----+---------+-------+
| id | int(4) | NO | PRI | NULL | |
| name | varchar(4) | NO | | NULL | |
| age | int(2) | NO | | NULL | |
+-------+------------+------+-----+---------+-------+
3 rows in set (0.011 sec)
注：CMD内执行命令，如果结束了必须得带上分号 ;9、 改变表的结构eg1 新增字段address
MariaDB [my]> alter table student add address varchar(48);
Query OK, 0 rows affected (0.007 sec)
Records: 0 Duplicates: 0 Warnings: 0
eg2 新增字段gender
MariaDB [my]> alter table student add gender enum("boy","girl") after age;
Query OK, 0 rows affected (0.008 sec)
Records: 0 Duplicates: 0 Warnings: 0
语句必须要正确，不然一定会报错。如下：
MariaDB [my]> alert table student add address varchar(48);
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near 'alert table student add address varchar(48)' at line 1
这里的错误是语句alter，这里打成了alert10、表结构改变成功后查看结构
MariaDB [my]> desc student;
+---------+--------------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+---------+--------------------+------+-----+---------+-------+
| id | int(4) | NO | PRI | NULL | |
| name | varchar(4) | NO | | NULL | |
| age | int(2) | NO | | NULL | |
| gender | enum('boy','girl') | YES | | NULL | |
| address | varchar(48) | YES | | NULL | |
+---------+--------------------+------+-----+---------+-------+
5 rows in set (0.007 sec)
11、修改表字段eg1 将gender修改为sex
MariaDB [my]> alter table student change gender sex enum("boy","girl") not null;
Query OK, 0 rows affected (0.014 sec)
Records: 0 Duplicates: 0 Warnings: 0
查看表结构信息
MariaDB [my]> desc student;
+---------+--------------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+---------+--------------------+------+-----+---------+-------+
| id | int(4) | NO | PRI | NULL | |
| name | varchar(4) | NO | | NULL | |
| age | int(2) | NO | | NULL | |
| sex | enum('boy','girl') | NO | | NULL | |
| address | varchar(48) | YES | | NULL | |
+---------+--------------------+------+-----+---------+-------+
5 rows in set (0.007 sec)