SQL Upvote Downvote system

inexperienced SQL user here.

I am currently working on a forum where posts need to have an upvote/downvote system.

My current sql(phpmyadmin) structure is like this:

Table 1 (posts) post_id | post_title | post_score

Table 2 (pvotes) pvote_id | fk_post_id | fk_user_id | pvote_score

I want to somehow make post_score (in table 1), find all pvote_score(table 2) collumns and add/subtract them together, where fk_post_id(table 2) is = to post_id(table 1)

This way i hope to make a voting system that only allows every user to vote once, and automatically calculate a posts post_score from the pvote_score values.

EDIT:

Sorry if question wasnt clear enough. I want to know how i can make the post_score collumn automatically add/subtract the values from pvotes_score and show the sum as its value

Thank you for your attention, hope you can help :-)

via Chebli Mohamed