cpanel: mysql database size 0MB

you may see the mysql database size as zero in cPanel >> ‘Mysql Databases’ option, though the databases contains tables and data. In order to include the size of the databases while displaying disk usage in cPanel/WHM, perform either of the following steps:
1) SSH to your server as root and edit the cpanel.config file

# vim /var/cpanel/cpanel.config

Search for

disk_usage_include_sqldbs=0

and change to

disk_usage_include_sqldbs=1

If the parameter is not present, add it. Save the file and execute the following command:

# /scripts/update_db_cache

OR
2) Login to the WHM, goto Tweak Settings >> ‘SQL’ section and enable the following option:

When displaying disk usage in cpanel/WHM include Postgresql and MySQL.

This will fix the issue.