数据库基础操作：

查看所有数据库

MariaDB [(none)]> show databases ;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| test               |
+--------------------+
4 rows in set (0.01 sec)

MariaDB [(none)]> #tree 
##查看数据库中的表
MariaDB [(none)]> show tables from mysql; 
    
#查看user表中的 user和host字段
MariaDB [(none)]> #select user,host from mysql.user;
MariaDB [(none)]> #显示出 user和host两个字段  在mysql数据库中 的user表中进行查找
MariaDB [(none)]> 
MariaDB [(none)]> select user,host from mysql.user;
+------+-----------+
| user | host      |
+------+-----------+
| root | 127.0.0.1 |
| root | ::1       |
|      | localhost |
| root | localhost |
|      | web01     |
| root | web01     |
+------+-----------+
6 rows in set (0.00 sec)             

只显示1条数据

MariaDB [(none)]> select * from mysql.user limit 1 ;
MariaDB [(none)]> select * from mysql.user limit 1 \G

whoami

select user();

pwd 显示当前使用的数据库

select database(); 

MariaDB [(none)]> select user,host from mysql.user ;
+------+-----------+
| user | host      |
+------+-----------+
| root | 127.0.0.1 |
| root | ::1       |
|      | localhost |
| root | localhost |
|      | web01     |
| root | web01     |
+------+-----------+
6 rows in set (0.00 sec)

MariaDB [(none)]> use mysql;
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A

Database changed
MariaDB [mysql]> select user,host from  user ;
+------+-----------+
| user | host      |
+------+-----------+
| root | 127.0.0.1 |
| root | ::1       |
|      | localhost |
| root | localhost |
|      | web01     |
| root | web01     |
+------+-----------+
6 rows in set (0.00 sec)

mysql  -uroot -p  -h172.16.1.7
mysql  -uroot -p  


MariaDB [(none)]> drop user ''@'localhost'; 
Query OK, 0 rows affected (0.00 sec)

MariaDB [(none)]> drop user ''@'web01'; 
Query OK, 0 rows affected (0.00 sec)

MariaDB [(none)]> 
MariaDB [(none)]> select user,host from  mysql.user ;
+-----------+------------+
| user      | host       |
+-----------+------------+
| root      | 127.0.0.1  |
| wordpress | 172.16.1.% |
| root      | ::1        |
| root      | localhost  |
| wordpress | localhost  |
| root      | web01      |
+-----------+------------+
6 rows in set (0.00 sec)

MariaDB [(none)]> 
MariaDB [(none)]> flush privileges;

[root@web01 ~]# mysqldump -uroot -p -A  >/root/all.sql 
Enter password: 


 mysqldump -uroot -p -A  >/root/all.sql 
 mysql -uroot -p     </root/all.sql 

[root@web01 ~]# mysqldump -uroot -p -A  |gzip  >/root/all-gzip.sql.gz
Enter password: 
[root@web01 ~]# ll /root/all-gzip.sql.gz 
-rw-r--r-- 1 root root 139656 Jun 10 11:21 /root/all-gzip.sql.gz
[root@web01 ~]# ll -h /root/all-gzip.sql.gz 
-rw-r--r-- 1 root root 137K Jun 10 11:21 /root/all-gzip.sql.gz