mysql-将多个表上的计数联接到查询

Question

I want to select columns from a table and a count bases on the join of another two table, how can I do it?

this is my count query which I have written:

   SELECT COUNT(*) AS num_review FROM approved_reviews  m, reviews u where 
   m.review_id_=u.id  and u.item_id =? and m.approved=1 

and I want to join it to

select item_id, item_name, item_price from items ?

how can I do it?

Answer 1

select items.item_id, item_name, item_price, COALESCE(t.cnt ,0)         
from items join (
                  SELECT u.item_id , COUNT(*) cnt
                  FROM approved_reviews  m, reviews u 
                  WHERE m.review_id_=u.id and m.approved=1
                  GROUP BY u.item_id 
                ) t on items.item_id = t.item_id

Answer 2

select * 
from
 (SELECT COUNT(*) AS num_review, u.item_id FROM approved_reviews  m, reviews u where 
   m.review_id_=u.id  and u.item_id =? and m.approved=1 group by u.item_id) count_sub, 
(select item_id, item_name, item_price from items) item_sub
where item_sub.item_id = count_sub.item_id