What Tool To Use

Hi guys! I was wondering if any of you know how I should work around this.

I am thinking of creating multiple databases and each database would have a different set of "usernames" but all database will have the same properties.

Is there any way that I can link all these databases into one master database so that I can just look up the username and all the databases & its info related to the username will show up for me?

A perfect example would be the Dynamic Search function in Google Sheets. Only reason why I would want to do this in Notion is because I want to post comments under the username, but I wouldn't want to comment under every single username across all the databases.