Using multiple COUNTs and SUMs in a single SQL statement

Question

I have a tables called pages, page_views, page_items and page_votes. The latter three tables contain a

Answer 1

This will select TOP 10 viewed pages, and will count items and votes only for these pages.

Efficient if you have lots of pages but need only 10 of them, eliminates unneeded counting.

SELECT  (
        SELECT COUNT(*)
        FROM   page_views
        WHERE  page_views.page_id = pages.id
        ) AS views_count,
        (
        SELECT COUNT(*)
        FROM   page_items
        WHERE  page_items.page_id = pages.id
        ) AS items_count,
        COALESCE(
        (
        SELECT SUM(vote)
        FROM   page_votes
        WHERE  page_votes.page_id = pages.id
        ), 0) AS votes_sum
FROM    pages
ORDER BY
        views_count DESC
LIMIT 10

Even more efficient query:

SELECT  pages.*,
        (
        SELECT COUNT(*)
        FROM   page_items
        WHERE  page_items.page_id = pages.id
        ) AS items_count,
        COALESCE(
        (
        SELECT SUM(vote)
        FROM   page_votes
        WHERE  page_votes.page_id = pages.id
        ), 0) AS votes_sum
FROM    (
        SELECT  page_id, COUNT(*) AS cnt
        FROM    page_views
        GROUP BY
                page_id
        ORDER BY cnt DESC
        LIMIT 10
        ) AS pvd,
        pages
WHERE  pages.id = pvd.page_id

, eliminates unneeded joins with pages.