mysqladmin -uroot -p12345 create testdb

#语法
# CREATE {DATABASE | SCHEMA} [IF NOT EXISTS] db_name

#方法一
CREATE DATABASE testdb;

#方法二，如果数据库已经存在则不返回错误信息，但是会有报警信息，可以使用SHOW warnings;来查看 
CREATE DATABASE IF NOT EXISTS testdb;


#方法三，创建数据库时指定字符集和排序规则
CREATE DATABASE four_honey
    CHARACTER SET utf8mb4
    COLLATE utf8mb4_unicode_ci;


# 查看数据库的字符集和排序规则
SELECT
    s.SCHEMA_NAME AS database_name,
    s.DEFAULT_CHARACTER_SET_NAME AS character_set,
    c.COLLATION_NAME AS collation
FROM
    information_schema.SCHEMATA s
JOIN
    information_schema.COLLATIONS c
    ON s.DEFAULT_COLLATION_NAME = c.COLLATION_NAME
WHERE
    s.SCHEMA_NAME = 'four_honey';

mysqladmin -uroot -p12345 drop testdb

DROP DATABASE testdb;

SHOW CREATE DATABASE testdb;

SHOW DATABASES; 

#语法
ALTER DATABASE DB_NAME character set utf8;

#范例
MariaDB [(none)]> ALTER DATABASE db1 character set utf8;
Query OK, 1 row affected (0.001 sec)

MariaDB [(none)]> show create database db1;
+----------+--------------------------------------------------------------+
| Database | Create Database ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? |
+----------+--------------------------------------------------------------+
| db1 ? ? | CREATE DATABASE `db1` /*!40100 DEFAULT CHARACTER SET utf8 */ |
+----------+--------------------------------------------------------------+ 1 row in set (0.000 sec)

[root@centos8 ~]#cat /var/lib/mysql/db1/db.opt 
default-character-set=utf8
default-collation=utf8_general_ci

DROP DATABASE|SCHEMA [IF EXISTS] 'DB_NAME';

MariaDB [(none)]> drop database db1;
Query OK, 0 rows affected (0.002 sec)

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

SELECT version();

USE testdb