Server version: 5.7.22-0ubuntu18.04.1 (Ubuntu)

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

mysql> update user set password=PASSWORD("1") where User='root';
ERROR 1046 (3D000): No database selected
mysql> 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
mysql> update user set password=PASSWORD("1") where User='root';
ERROR 1054 (42S22): Unknown column 'password' in 'field list'
mysql> SET PASSWORD FOR 'root'@'localhost' = PASSWORD('1');
Query OK, 0 rows affected, 2 warnings (0.01 sec)

mysql> flush privileges;
Query OK, 0 rows affected (0.00 sec)

# sudo mysql_secure_installation 
 
Securing the MySQL server deployment. 
                                                                                                                                                                                                                                              
Connecting to MySQL using a blank password.                                                                                                                                                                                                   
The 'validate_password' plugin is installed on the server.                                                                                                                                                                                    
The subsequent steps will run with the existing configuration                                                                                                                                                                                 
of the plugin.                                                                                                                                                                                                                                
Please set the password for root here.                                                                                                                                                                                                        
                                                                                                                                                                                                                                              
New password:                                                                                                                                                                                                                                 
                                                                                                                                                                                                                                              
Re-enter new password:                                                                                                                                                                                                                        
                                                                                                                                                                                                                                              
Estimated strength of the password: 0                                                                                                                                                                                                         
Do you wish to continue with the password provided?(Press y|Y for Yes, any other key for No) : Y                                                                                                                                              
By default, a MySQL installation has an anonymous user,                                                                                                                                                                                       
allowing anyone to log into MySQL 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? (Press y|Y for Yes, any other key for No) : k 
 
 ... skipping. 
 
 
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? (Press y|Y for Yes, any other key for No) : n 
 
 ... skipping. 
By default, MySQL 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? (Press y|Y for Yes, any other key for No) : n 
 
 ... skipping. 
Reloading the privilege tables will ensure that all changes 
made so far will take effect immediately. 
 
Reload privilege tables now? (Press y|Y for Yes, any other key for No) : y 
Success. 
 
All done! 

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

mysql> SELECT user,authentication_string,plugin,host FROM mysql.user;
+------------------+-------------------------------------------+-----------------------+-----------+
| user             | authentication_string                     | plugin                | host      |
+------------------+-------------------------------------------+-----------------------+-----------+
| root             |                                           | auth_socket           | localhost |
| mysql.session    | *THISISNOTAVALIDPASSWORDTHATCANBEUSEDHERE | mysql_native_password | localhost |
| mysql.sys        | *THISISNOTAVALIDPASSWORDTHATCANBEUSEDHERE | mysql_native_password | localhost |
| debian-sys-maint | *57A7D3C520B6878F27738F51372311884DBF2566 | mysql_native_password | localhost |
| phpmyadmin       | *E6CC90B878B948C35E92B003C792C46C58C4AF40 | mysql_native_password | localhost |
+------------------+-------------------------------------------+-----------------------+-----------+
5 rows in set (0.01 sec)

mysql> ALTER USER 'root'@'localhost' IDENTIFIED WITH mysql_native_password BY '1';
ERROR 1819 (HY000): Your password does not satisfy the current policy requirements
mysql> ALTER USER 'root'@'localhost' IDENTIFIED WITH mysql_native_password BY '97531';
ERROR 1819 (HY000): Your password does not satisfy the current policy requirements
mysql> ALTER USER 'root'@'localhost' IDENTIFIED WITH mysql_native_password BY 'a9b7b5b3b1';
ERROR 1819 (HY000): Your password does not satisfy the current policy requirements
mysql> ALTER USER 'root'@'localhost' IDENTIFIED WITH mysql_native_password BY 'a9&b7b&5b3b1';
ERROR 1819 (HY000): Your password does not satisfy the current policy requirements