My question is similar to this one: Compare rows and get percentage

However, little different. I adapted my question to the other post.

I got 2 tables.

First table:

user_id | post_id
1         1
1         2
1         3
2         12
2         15

And second table:

post_id | rating
1         1
1         2
1         3 
2         1
2         5
3         null
3         1
3         4
12        4
15        1

So now I would like to count the rating for each post, in the second table. If the rating has more than, lets say, 50% positive ratings than I want to get the post_id and going it to the post_id from table one and add 1 to the user_id.

At the end it would return the user_id with the number of positive posts.

The result for above table would be:

user_id | helpfulPosts
1         2
2         1

The post with post_id 1 and 3 have positive rating, because more than 50% have ratings of 1-3. The post with id = 2 is not positive, because the rating is exactly 50%.

How would I achieve this?

For clarification: It's a mysql rdbm and a positive post, is one where the number of rating_ids with 1, 2 and 3 are more than half of the overall rating. Basically the same thing, from the other thread I posted above.