part_id  |  part_name

post_id | part_id | type | title | content

part_id | part_name | count_posts_type1 | count_posts_type2 | count_posts_type3

select
pa.part_id, pa.part_name,
coalesce(sum(case when po.type = 1 then 1 else 0 end), 0) as count_posts_type1,
coalesce(sum(case when po.type = 2 then 1 else 0 end), 0) as count_posts_type2,
coalesce(sum(case when po.type = 3 then 1 else 0 end), 0) as count_posts_type3
from parts pa
left join posts po on po.part_id = pa.part_id
group by pa.part_id, pa.part_name

SELECT
     parts.part_id,
     parts.part_name,
     COUNT(t1.post_id) AS count_posts_type1,
     COUNT(t2.post_id) AS  count_posts_type2,
     COUNT(t3.post_id) AS count_posts_type3
FROM posts
     RIGHT JOIN part ON posts.part_id=parts.part_id
     INNER JOIN ( SELECT post_id FROM posts WHERE type=1 ) as t1(post_id) ON posts.post_id = t1.post_id
     INNER JOIN ( SELECT post_id FROM posts WHERE type=1 ) as t2(post_id) ON posts.post_id = t2.post_id
     INNER JOIN ( SELECT post_id FROM posts WHERE type=1 ) as t3(post_id) ON posts.post_id = t3.post_id