how to set specific variables from external database in mailchimp campaign

I am very new to email marketing and I would really appreciate the help.

Right now I want to create a campaign via API to an audience using a template. And in this template I want to use specific variables from my database. This variables are dynamic (change day by day) and different to each user. That is why I can not set it in my audience merge tags

Do you if this it is possible? and if it is, how could achieve it?

Thank you in advance