I'm a bit confused as to which database I'm actually running.

mysql output -

tom@gqmvjh2 ~ $ mysql -u tom -p
Enter password:
Welcome to the MariaDB monitor. Commands end with ; or \g.
Your MariaDB connection id is 167
Server version: 10.0.31-MariaDB-0ubuntu0.16.04.2 Ubuntu 16.04

Copyright (c) 2000, 2017, Oracle, MariaDB Corporation Ab and others.

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

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]> show variables like "%version%";
+-------------------------+----------------------------------+
| Variable_name | Value |
+-------------------------+----------------------------------+
| innodb_version | 5.6.36-82.0 |
| protocol_version | 10 |
| slave_type_conversions | |
| version | 10.0.31-MariaDB-0ubuntu0.16.04.2 |
| version_comment | Ubuntu 16.04 |
| version_compile_machine | x86_64 |
| version_compile_os | debian-linux-gnu |
| version_malloc_library | bundled jemalloc |
+-------------------------+----------------------------------+
8 rows in set (0.00 sec)

MariaDB [mysql]>

cqrlog debug level 1 output -

tom@gqmvjh2 ~ $ cqrlog --debuglevel = 1

**** DEBUG LEVEL 1 ****

SSL libraries:
/lib/x86_64-linux-gnu/libssl.so.1.0.0
/lib/x86_64-linux-gnu/libcrypto.so.1.0.0
Loading libmysqlclient: /usr/lib/x86_64-linux-gnu/libmysqlclient.so.20.3.6
**************************
MySQL version: 5.7
**************************
**********************************
MySQL version assigned: 5.7
**********************************

phpmyadmin says -

Server: Localhost via UNIX socket
Server type: MariaDB
Server version: 10.0.31-MariaDB-0ubuntu0.16.04.2 - Ubuntu 16.04
Protocol version: 10
User: tom@localhost
Server charset: UTF-8 Unicode (utf8)

Synaptics package manager indicates mariadb is installed and mysql is NOT installed.

Perhaps someone can sort this out?

Regards,
Tom