如何在SQL ..中查找给定文章的评论计数和审阅计数？

Question

I have 2 tables :

• review (including content_type_id , object_id )
• comments (including content_type_id , object_id )

---

The combination of " content_type_id and object_id " uniquely defines an entity (like article etc)

---

Now i want to write a single SQL Query to :

"list all the articles with their 'review_count' and 'comment_count' ".

I mean in final result , what i want is :

content_type_id | object_id | review_count | comment_count

How can i acheive this..??

Answer 1

(Edited after question changed and I found a data-bug)

Try this one:

select 
    content_type_id, object_id,
    sum(review_count) review_count,
    sum(comment_count) comment_count
from
    (
        select 
            content_type_id, object_id, count(*) review_count 
        from jc_reviews 
        group by 1, 2
    ) as r_count
    full outer join 
    ( 
        select content_type_id, object_id, count(*) comment_count 
        from jc_comments 
        group by 1, 2
    ) as c_count
    using (content_type_id, object_id)
group by 1, 2

It does not use a central table (formerly called article ). This means, that items without any comment and without any review will not show up in the result. Items where at least one comment or one review is there will show up.

Answer 2

SELECT article_id, article_name,
(
    select count(review_id)
    from review 
    where article_id = a.articles
) review_count,
(
   select count(comments _id)
    from comments 
    where article_id = a.articles
) comment_count
FROM articles a

Answer 3

Off the top of my head but I think it would work:

SELECT
article_id,
article_name,
count(review_id) as review_count,
count(comment_id) as comment_count
FROM articles a, reviews b, comments c
WHERE
a.article_id = b.article_id OR
a.article_id = c.article_id

This would go only for articles with reviews and/or comments. To get ones without use a left join.

Answer 4

select a.article_id,
    coalesce(rc.review_count, 0) as review_count,
    coalesce(cc.comment_count, 0) as comment_count
from articles a
left outer join (
    select article_id, count(*) as review_count
    from review
    group by article_id
) rc on a.article_id = rc.article_id
left outer join (
    select article_id, count(*) as comment_count
    from comments
    group by article_id
) cc on a.article_id = cc.article_id

Answer 5

I would begin by keeping a consistent naming convention on my tables and keep them all named in the singular

SELECT article_id = a.article_id
       ,review_count = COUNT(DISTINCT(r.review_id))
       ,comment_count = COUNT(DISTINCT(c.comment_id))
  FROM article a
  LEFT OUTER JOIN review r
    ON a.article_id = r.article_id
  LEFT OUTER JOIN comment c
    ON a.article_id = c.article_id
 GROUP BY a.article_id

Here's some test data to play with:

-- Create tables
CREATE TABLE article(article_id INT)
CREATE TABLE review(review_id INT, article_id INT)
CREATE TABLE comment(comment_id INT, article_id INT)

-- Create some test data
INSERT INTO article SELECT 1
INSERT INTO article SELECT 2
INSERT INTO article SELECT 3

INSERT INTO review SELECT 10, 1
INSERT INTO review SELECT 20, 2
INSERT INTO review SELECT 30, 2
INSERT INTO review SELECT 40, 3
INSERT INTO review SELECT 50, 3
INSERT INTO review SELECT 60, 3

INSERT INTO comment SELECT 200, 1
INSERT INTO comment SELECT 300, 1
INSERT INTO comment SELECT 400, 2
INSERT INTO comment SELECT 500, 2
INSERT INTO comment SELECT 600, 3

After you significantly changed your question, I believe this query will provide you an answer:

SELECT u.content_type_id
       ,u.object_id
       ,review_count = SUM(u.review_count)
       ,comment_count = SUM(u.comment_count)
  FROM
    (
    SELECT content_type_id
           ,object_id
           ,review_count = COUNT(*)
           ,comment_count = 0
      FROM review
     GROUP BY content_type_id, object_id
     UNION
    SELECT content_type_id
           ,object_id
           ,review_count = 0
           ,comment_count = COUNT(*)
      FROM comment
     GROUP BY content_type_id, object_id
    ) u
GROUP BY u.content_type_id, u.object_id

And here is some test data to work with:

CREATE TABLE review(review_id INT, content_type_id INT, object_id INT)
CREATE TABLE comment(comment_id INT, content_type_id INT, object_id INT)

INSERT INTO review SELECT 11, 10, 100
INSERT INTO review SELECT 12, 10, 100
INSERT INTO review SELECT 13, 20, 100
INSERT INTO review SELECT 13, 10, 200
INSERT INTO review SELECT 13, 30, 100
INSERT INTO comment SELECT 21, 10, 100
INSERT INTO comment SELECT 22, 20, 100
INSERT INTO comment SELECT 23, 20, 100
INSERT INTO comment SELECT 24, 20, 100
INSERT INTO comment SELECT 25, 10, 200
INSERT INTO comment SELECT 26, 10, 200

Answer 6

try this:

SELECT  a.Article_ID,
        COUNT(b.Article_ID) as ReviewCount,
        COUNT(c.Article_ID) as CommentCount
FROM Articles a JOIN Review b ON
        a.Article_ID = b.Article_ID
    LEFT JOIN Comments c ON
        a.Article_ID = c.Article_ID
GROUP BY a.Article_ID