How to query the name of each section and the number of threads at it using sql query? - sql

Question

I have 2 tables at mysql database the first one contains parts like this:
parts
primary part_name part_id
0 web 1
0 graphic 2
1 php 3
1 asp 4
2 photoshop 5
2 illustrator 6
1 html 7
some of parts are primary like web, graphic. and others are subsections
for example web section contains (php,asp,html) parts
so at primary field there is the id of father part
graphic part contains (photoshop, illustrator) parts.
the other table is for posts;
posts
post_content post_title part_id post_id
anything any title 3 1
anything any title 6 2
anything any title 3 3
anything any title 3 4
anything any title 7 5
anything any title 6 6
anything any title 4 7
anything any title 4 8
anything any title 3 9
I want to get a table contains the main parts (primary = 0)
and sum of posts at it
the result should be like this;
query result
count_posts part_name part_id
7 web 1
2 graphic 2
I tried this:
SELECT p.*,count(s.post_id)
FROM part p,post s
where s.part_id = 1
and p.belong = 1
but it get results only for one part

Answer 1

Can't yet comment on other posts than my own so I'm submiting a new answer.
#StuartLC answer is missing the join between primary parts and subsections.
SELECT COUNT(po.post_id) AS count_posts, pa.part_name, pa.part_id
FROM parts pa
INNER JOIN parts pa2 on pa2.[primary] = pa.part_id
INNER JOIN posts po on po.part_id = pa2.part_id
WHERE pa.[primary] = 0
GROUP BY pa.part_name, pa.part_id
http://sqlfiddle.com/#!6/1dd90/3/0