On 12/03/2010 12:40 PM, Jayadevan M wrote:
Hello,
I went this way, but for a large number of user_id's, it's quite slow:
CREATE VIEW v_views AS
SELECT user_id, product_id, count(*) as views
FROM viewlog
GROUP BY user_id, product_id
SELECT
DISTINCT user_id,
(SELECT product_id FROM v_views inn WHERE inn.user_id = out.user_id
ORDER BY views DESC LIMIT 1) as product_id,
(SELECT views FROM v_views inn WHERE inn.user_id = out.user_id ORDER
BY
views DESC LIMIT 1) as views
FROM
v_views out
Does this work faster?
select x.user_id,y.product_id,x.count from
(select user_id, max(count ) as count from (select user_id,product_id,
count(*) as count from viewlog group by user_id,product_id) as x group by
user_id
) as x inner join
(select user_id,product_id, count(*) as count1 from viewlog group by
user_id,product_id ) as y
on x.user_id=y.user_id and x.count=y.count1
The issue in both approaches is that if I have two product_ids that are
viewed same number of times and share the first place as most viewed
products by that user, I'll get only one of them (LIMIT 1 OR MAX() can
only return one row :).
I don't see how I can sort this out with elegance in SQL.
Mario
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