给mysql设置登录密码为123

[root@win10 ~]# mysql -uroot -p 
Enter password: 
Welcome to the MariaDB monitor. Commands end with ; or \g. 
Your MariaDB connection id is 8 
Server version: 10.3.17-MariaDB MariaDB Server 
Copyright (c) 2000, 2018, Oracle, MariaDB Corporation Ab and others.
Type ‘help;‘ or ‘\h‘ for help. Type ‘\c‘ to clear the current input statement.

MariaDB [(none)]> set password = password(‘123‘); #后面的password是加密 
Query OK, 0 rows affected (0.000 sec)

修改mysql登录密码

[root@test ~]# mysql -uroot -p123
Welcome to the MariaDB monitor.  Commands end with ; or \g.
Your MariaDB connection id is 21
Server version: 10.3.17-MariaDB MariaDB Server

Copyright (c) 2000, 2018, Oracle, MariaDB Corporation Ab and others.

Type ‘help;‘ or ‘\h‘ for help. Type ‘\c‘ to clear the current input statement.

MariaDB [(none)]> alter user ‘root‘@‘localhost‘ identified by ‘123456‘;
Query OK, 0 rows affected (0.000 sec)

MariaDB [(none)]> quit
Bye
[root@test ~]# mysql -uroot -p123456
Welcome to the MariaDB monitor.  Commands end with ; or \g.
Your MariaDB connection id is 22
Server version: 10.3.17-MariaDB MariaDB Server

Copyright (c) 2000, 2018, Oracle, MariaDB Corporation Ab and others.

Type ‘help;‘ or ‘\h‘ for help. Type ‘\c‘ to clear the current input statement.
MariaDB [(none)]> 

mysql_secure_installation //安全初始化

[root@test ~]# mysql_secure_installation 

NOTE: RUNNING ALL PARTS OF THIS SCRIPT IS RECOMMENDED FOR ALL MariaDB
      SERVERS IN PRODUCTION USE!  PLEASE READ EACH STEP CAREFULLY!

In order to log into MariaDB to secure it, we‘ll need the current
password for the root user.  If you‘ve just installed MariaDB, and
you haven‘t set the root password yet, the password will be blank,
so you should just press enter here.

Enter current password for root (enter for none):   输入root账户的密码

Change the root password? [Y/n]  y  是否改变root密码
New password: 
Re-enter new password: 
Password updated successfully!
Reloading privilege tables..
 ... Success!


By default, a MariaDB installation has an anonymous user, allowing anyone
to log into MariaDB without having to have a user account created for
them.  This is intended only for testing, and to make the installation
go a bit smoother.  You should remove them before moving into a
production environment.

Remove anonymous users? [Y/n] y  要不要移除匿名账户
 ... Success!

Normally, root should only be allowed to connect from ‘localhost‘.  This
ensures that someone cannot guess at the root password from the network.

Disallow root login remotely? [Y/n] n 要不要设置不允许root账户远程登陆
 ... skipping.

By default, MariaDB comes with a database named ‘test‘ that anyone can
access.  This is also intended only for testing, and should be removed
before moving into a production environment.

Remove test database and access to it? [Y/n] y 要不要移除测试数据库和访问它的权限
- Dropping test database...
 ... Success!
 - Removing privileges on test database...
 ... Success!

Reloading the privilege tables will ensure that all changes made so far
will take effect immediately.

Reload privilege tables now? [Y/n] y 要不要重新加入权限表
 ... Success!

Cleaning up...

All done!  If you‘ve completed all of the above steps, your MariaDB
installation should now be secure.

Thanks for using MariaDB!

两种查看数据库的方法

[root@test ~]# mysql -uroot -p123123
Welcome to the MariaDB monitor.  Commands end with ; or \g.
Your MariaDB connection id is 32
Server version: 10.3.17-MariaDB MariaDB Server

Copyright (c) 2000, 2018, Oracle, MariaDB Corporation Ab and others.

Type ‘help;‘ or ‘\h‘ for help. Type ‘\c‘ to clear the current input statement.

MariaDB [(none)]>  show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
+--------------------+
3 rows in set (0.004 sec)

MariaDB [(none)]> quit
Bye
.................................................................

[root@test ~]#  mysql -uroot -p123123 -e ‘show databases;‘
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
+--------------------+

DDL操作

创建数据库

MariaDB [(none)]> CREATE DATABASE IF NOT EXISTS school;
Query OK, 1 row affected (0.000 sec)

MariaDB [(none)]> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| school             |
+--------------------+
4 rows in set (0.000 sec)

MariaDB [(none)]> 

删除数据库

MariaDB [(none)]> DROP DATABASE IF EXISTS school;
Query OK, 0 rows affected (0.005 sec)

MariaDB [(none)]> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
+--------------------+
3 rows in set (0.000 sec)

MariaDB [(none)]> 

表操作

创建一个空表

MariaDB [(none)]> CREATE DATABASE IF NOT EXISTS school;
Query OK, 1 row affected (0.000 sec)

MariaDB [(none)]> use school;
Database changed
MariaDB [school]> show tables;
Empty set (0.000 sec)

MariaDB [school]> CREATE TABLE student(id int not null,name varchar(50)null,age tinyint );
Query OK, 0 rows affected (0.004 sec)

MariaDB [school]> show tables;
+------------------+
| Tables_in_school |
+------------------+
| student          |
+------------------+
1 row in set (0.000 sec)

MariaDB [school]> 

查看表的结构

MariaDB [school]> DESC student;
+-------+-------------+------+-----+---------+-------+
| Field | Type        | Null | Key | Default | Extra |
+-------+-------------+------+-----+---------+-------+
| id    | int(11)     | NO   |     | NULL    |       |
| name  | varchar(50) | YES  |     | NULL    |       |
| age   | tinyint(4)  | YES  |     | NULL    |       |
+-------+-------------+------+-----+---------+-------+
3 rows in set (0.002 sec)

MariaDB [school]> 

获取创建表的帮助

MariaDB [school]> help create table;
Name: ‘CREATE TABLE‘
Description:
Syntax:
CREATE [TEMPORARY] TABLE [IF NOT EXISTS] tbl_name
    (create_definition,...)
    [table_options]
    [partition_options]

Or:

CREATE [TEMPORARY] TABLE [IF NOT EXISTS] tbl_name
    [(create_definition,...)]
    [table_options]
    [partition_options]
    select_statement

Or:

CREATE [TEMPORARY] TABLE [IF NOT EXISTS] tbl_name
    { LIKE old_tbl_name | (LIKE old_tbl_name) }

create_definition:
    col_name column_definition
  | [CONSTRAINT [symbol]] PRIMARY KEY [index_type] (index_col_name,...)
      [index_option] ...
  | {INDEX|KEY} [index_name] [index_type] (index_col_name,...)
      [index_option] ...
  | [CONSTRAINT [symbol]] UNIQUE [INDEX|KEY]
      [index_name] [index_type] (index_col_name,...)
      [index_option] ...
  | {FULLTEXT|SPATIAL} [INDEX|KEY] [index_name] (index_col_name,...)
      [index_option] ...
  | [CONSTRAINT [symbol]] FOREIGN KEY
      [index_name] (index_col_name,...) reference_definition
  | CHECK (expr)

column_definition:
    data_type [NOT NULL | NULL] [DEFAULT default_value]
      [AUTO_INCREMENT] [UNIQUE [KEY] | [PRIMARY] KEY]
      [COMMENT ‘string‘]
      [COLUMN_FORMAT {FIXED|DYNAMIC|DEFAULT}]
      [STORAGE {DISK|MEMORY|DEFAULT}]
      [reference_definition]
...
...
...

修改表，加入班级class

MariaDB [school]> DESC student;
+-------+-------------+------+-----+---------+-------+
| Field | Type        | Null | Key | Default | Extra |
+-------+-------------+------+-----+---------+-------+
| id    | int(11)     | NO   |     | NULL    |       |
| name  | varchar(50) | YES  |     | NULL    |       |
| age   | tinyint(4)  | YES  |     | NULL    |       |
+-------+-------------+------+-----+---------+-------+
3 rows in set (0.001 sec)

MariaDB [school]> ALTER TABLE student ADD class varchar(20);
Query OK, 0 rows affected (0.004 sec)
Records: 0  Duplicates: 0  Warnings: 0

MariaDB [school]> desc student;
+-------+-------------+------+-----+---------+-------+
| Field | Type        | Null | Key | Default | Extra |
+-------+-------------+------+-----+---------+-------+
| id    | int(11)     | NO   |     | NULL    |       |
| name  | varchar(50) | YES  |     | NULL    |       |
| age   | tinyint(4)  | YES  |     | NULL    |       |
| class | varchar(20) | YES  |     | NULL    |       |
+-------+-------------+------+-----+---------+-------+
4 rows in set (0.002 sec)

删除age

MariaDB [school]> ALTER TABLE student DROP age;
Query OK, 0 rows affected (0.009 sec)
Records: 0  Duplicates: 0  Warnings: 0

MariaDB [school]> desc student;
+-------+-------------+------+-----+---------+-------+
| Field | Type        | Null | Key | Default | Extra |
+-------+-------------+------+-----+---------+-------+
| id    | int(11)     | NO   |     | NULL    |       |
| name  | varchar(50) | YES  |     | NULL    |       |
| class | varchar(20) | YES  |     | NULL    |       |
+-------+-------------+------+-----+---------+-------+
3 rows in set (0.001 sec)

MariaDB [school]> 

删除表

MariaDB [school]> show tables;
+------------------+
| Tables_in_school |
+------------------+
| student          |
+------------------+
1 row in set (0.000 sec)

MariaDB [school]> DROP TABLE student;
Query OK, 0 rows affected (0.003 sec)

MariaDB [school]> show tables;
Empty set (0.000 sec)

MariaDB [school]> 

DML操作

DML操作包括增(INSERT)、删(DELETE)、改(UPDATE)、查(SELECT)，均属针对表的操作。

MariaDB [school]> DESC student;          查看表的结构
+-------+-------------+------+-----+---------+-------+
| Field | Type        | Null | Key | Default | Extra |
+-------+-------------+------+-----+---------+-------+
| id    | int(11)     | NO   |     | NULL    |       |
| name  | varchar(50) | YES  |     | NULL    |       |
| age   | tinyint(4)  | YES  |     | NULL    |       |
+-------+-------------+------+-----+---------+-------+
3 rows in set (0.003 sec)

MariaDB [school]> ALTER TABLE student ADD class varchar(20);
Query OK, 0 rows affected (0.005 sec)
Records: 0  Duplicates: 0  Warnings: 0

MariaDB [school]> DESC student;
+-------+-------------+------+-----+---------+-------+
| Field | Type        | Null | Key | Default | Extra |
+-------+-------------+------+-----+---------+-------+
| id    | int(11)     | NO   |     | NULL    |       |
| name  | varchar(50) | YES  |     | NULL    |       |
| age   | tinyint(4)  | YES  |     | NULL    |       |
| class | varchar(20) | YES  |     | NULL    |       |
+-------+-------------+------+-----+---------+-------+
4 rows in set (0.001 sec)

增操作insert

MariaDB [school]>                         在表里面加入数据
MariaDB [school]> INSERT INTO student (id,name,age,class) VALUE (1,‘taochi‘,5,5),(2,‘chensongling‘,20,6),(3,‘wangming‘,21,5),(4,‘fangxinxin‘,18,7);
Query OK, 4 rows affected (0.007 sec)
Records: 4  Duplicates: 0  Warnings: 0

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