Question

I have 2 tables :

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

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

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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.