If your MySQL database is not correctly configured for Ghost then you may run into some issues.

Error message:

ER_WRONG_FIELD_WITH_GROUP

...which is not functionally dependent on columns in GROUP BY clause; this is incompatible with sql_mode=only_full_group_by...

To fix:

1. Open your my.cnf using sudo find / -name my.cnf
2. Remove only_full_group_by from mysql_mode

This solution is for self-hosted Ghost developers who are using the supported install method with ghost-cli. If you're having problems with an unsupported custom install, or check out the forum.