Issue
I have one table (posts) with articles and article meta.
Another table (post_reviews) contains user-submitted ratings (a value out of 5) for each article, referencing posts by the id of the post in question.
I am trying to find the top three posts, by review, of the last 3 days. Therefore I need to:
find all the posts in that time period (3 days)
find the average rating for each post
sort them by average rating (desc)
Code
For the first part, I can successfully use the query:
SELECT * FROM `posts` WHERE `hub_id`=:hub_id AND `date`>=:start_date AND `date`<=:end_date)
To find each individual post's average rating, I use this query:
SELECT SUM(`review`) AS `total` FROM `post_reviews` WHERE `id`=:id
then get the number of rows from this to work out the average:
SELECT * FROM `post_reviews` WHERE `post_id`=:id
How can I combine these three, or process this data so I can order the posts in a time period by the average rating?
ANSWER
The end result looks like this:
SELECT `posts`.`id`, avg(`post_reviews`.`review`) as `average`
FROM `posts`
JOIN `post_reviews` ON (`posts`.`id`=`post_reviews`.`post_id`)
WHERE `hub_id`=:hub_id
AND `posts`.`date`>=:start_date
AND `posts`.`date`<=:end_date
GROUP BY `post_id`
ORDER BY avg(`review`) desc
Not sure what your hub_id represents, but I assume it's necessary; also assume the key field in Posts is posts.post_id and not posts.id:
SELECT `p`.`id`, avg(`pr`.`review`) AS `average`
FROM `posts` AS `p`
JOIN `post_reviews` AS `pr` ON (`p`.`id`=`pr`.`post_id`)
WHERE `hub_id` =:hub_id
AND `p`.`date` BETWEEN CURRENT_DATE-3 AND CURRENT_DATE
GROUP BY `p`.`id`
ORDER BY avg(`review`) DESC;
See Example: sqlfiddle
Not sure about the syntax for MySQL, but the would need a join and a group by.
Something like....
SELECT post_id. avg(review)
FROM Posts P Inner Join Post_reviews PR on (p.post_id = pr.Post_id)
WHERE `hub_id`=:hub_id AND `date`>=:start_date AND `date`<=:end_date)
Group by Post_id
order by 2 desc
Here is a query that works with sqlfiddle to prove it.
SELECT
p.hub_id
,p.post_id
,p.article
,p.articleMeta
,p.date
,IFNULL(AVG(r.ratings), 0) averageRating
FROM posts p
LEFT JOIN post_reviews r ON
r.post_id = p.post_id
WHERE
hub_id = 1
AND date >= CURDATE() - 3
AND date <= CURDATE()
GROUP BY
p.hub_id
,p.post_id
,p.article
,p.articleMeta
,p.date
ORDER BY
p.date DESC
,averageRating DESC
http://sqlfiddle.com/#!2/39315/1
Related
Yesterday I tried to retrieve data from my db table using 'user_id' as a criterion to limit the amount of data per user.
I tried to get data from table https://prnt.sc/p53zhp in format like this https://prnt.sc/p541wk and limit the number of output records for user_id where limit will be 2 (count(user_id) <= 2), but i don't understand how to do that. What kind of sql request can i use to get this data?
Assuming that your RDBMS, here is a solution yo select only the top 2 records per user. You can use ROW_NUMBER() in a subquery to rank records by id within groups of records having the same user_id, and the filter out unerelevant records in the outer query, like:
SELECT *
FROM (
SELECT
t.*,
ROW_NUMBER() OVER(PARTITION BY user_id ORDER BY id)
FROM mytable
) x WHERE rn <= 2
On earlier versions of MySQL, you could use self-LEFT JOIN the table and use GROUP BY and HAVING COUNT(...) < 2 to limit the results to first two records per group:
SELECT
t.id,
t.user_id,
t.vip,
t.title,
t.description,
t.data
FROM mytable t
LEFT JOIN mytable t1 ON t1.user_id = t.user_id AND t1.id > t.id
GROUP BY
t.id,
t.user_id,
t.vip,
t.title,
t.description,
t.data
HAVING COUNT(t1.id) < 2
I don't understand if your problem is a Transact-SQL or your code.
In SQL you can limit record with "LIMIT": https://www.w3schools.com/sql/sql_top.asp
In code, you can use a condition IF.
i am trying to get all topics based on a forum ID.
Those topics need to be ordered by sticky first and then by last post date secondly.
I have this query, working almost fine but it doesn't order the topics in the way i want.
SELECT
forum_posts.posted_by,
forum_posts.posted,
forum_topics.id,
forum_topics.subject,
forum_topics.sticky,
forum_topics.closed
FROM
forum_posts
LEFT JOIN
forum_topics
ON
forum_topics.id=forum_posts.topic_id
WHERE forum_topics.forum_id=$forumdata->id
GROUP BY forum_topics.id
ORDER BY forum_posts.posted DESC
If I read your question correctly, then you only need to make a slight change to the ORDER BY clause:
ORDER BY
forum_topics.sticky, -- just add this
forum_posts.posted DESC;
However, as you are selecting non aggregate columns, my hunch is that you should really be using a subquery to figure out the latest post:
SELECT
ft.*, fp1.*
FROM forum_posts fp1
INNER JOIN
(
SELECT topic_id, MAX(posted) AS max_posted
FROM forum_posts
GROUP BY topic_id
) fp2
ON fp1.topic_id = fp2.topic_id AND
fp1.posted = fp2.max_posted
LEFT JOIN forum_topics ft
ON fp1.id = ft.topic_id
ORDER BY
ft.sticky;
if you need sticky first an then post then you need order by orum_topics.sticky, forum_posts.posted eg:
SELECT
forum_posts.posted_by,
forum_posts.posted,
forum_topics.id,
forum_topics.subject,
forum_topics.sticky,
forum_topics.closed
FROM
forum_posts
LEFT JOIN
forum_topics
ON
forum_topics.id=forum_posts.topic_id
WHERE forum_topics.forum_id=$forumdata->id
GROUP BY forum_topics.id
ORDER BY forum_topics.sticky DESC, forum_posts.posted DESC
I have two tables one for topic_likes & one for user_comments.I must get recent updates of like & comment from this tables.Given below is the sql :-
SELECT (required fields...)
LEFT JOIN topic_likes AS TL ON (TL.delete_status=0 AND TL.user_id!=$user_id)
LEFT JOIN user_comments AS UC ON (UC.delete_status=0 AND UC.user_id!=$user_id)
WHERE
(TL.created_date >= '$lastLogin' OR UC.created_date >= '$lastLogin'
ORDER BY UC.created_date desc,TL.created_date desc
LIMIT $limit
I have given order by two fields from two tables(UC.created_date, TL.created_date)
But it does not order the resultset based on created_date from topic_likes.It only orders the results based on user_comments table
But if I removed the limit condition it gives correct results...!!
Any suggestion appreciated
This is a strange approach you're taking. If you want to display user's likes and comments using a single query you should UNION the results. Example:
SELECT * FROM
(
SELECT id, `date`, 'like' as `type` FROM topic_likes
UNION
SELECT id, `date`, 'comment' as `type` FROM user_comments
) a order by a.date DESC limit 5;
The result should be similar to this:
But there are limitations. The number of columns from each subquery must match.
I have a table categories and table posts . I want to return categories that have more than 3 posts.
My query
SELECT `categories`.`category_title`, COUNT(posts.post_id) as total_posts
FROM (`categories`)
JOIN `posts` ON `posts`.`category_id` = `categories`.`category_id`
HAVING `total_posts` > 3
ORDER BY `categories`.`date_created` desc
it returns just 1 row.. What is the correct way to do this type of query without using 2 queries?
Your query is making use of a MySQL feature called "hidden columns" and you might not even know it. This is because your query is referencing elements, such as date_created, which should be aggregated but are not ("should" here means according to the SQL standard and most other databases).
The problem with your query is that it is missing the group by. An alternative way of writing this is with the aggregation in a subquery, before joining to category:
SELECT `categories`.`category_title`, total_posts
FROM `categories` JOIN
(select categoryid, COUNT(posts.post_id) as total_posts
from `posts`
group by categoryid
having count(*) > 3
) pc
ON `pc`.`category_id` = `categories`.`category_id`
ORDER BY `categories`.`date_created` desc
You need to group the items by category.
SELECT `categories`.`category_title`, COUNT(posts.post_id) as total_posts
FROM (`categories`)
JOIN `posts` ON `posts`.`category_id` = `categories`.`category_id`
GROUP BY `categories`.`category_id`
HAVING `total_posts` > 3
ORDER BY `categories`.`date_created` desc
I have a query to pull all articles out of the database..
$get_articles = $db->query("
SELECT *, a.id AS id, s.type AS type FROM ".$prefix."articles a
LEFT JOIN ".$prefix."sources s ON (s.id = source_id)
WHERE a.type!='trashed' ORDER BY a.timestamp DESC LIMIT $start, $end");
Within the loop of this query, I do then do another query on the same table to find related articles to the 'title' of the article, stored as '$related_phrase'. The query within the loop is:
// get related articles to this entry
$get_related = $db->query("
SELECT *, a.id AS id, MATCH (title, description) AGAINST ('$related_phrase') AS score FROM ".$prefix."articles a
LEFT JOIN ".$prefix."sources s ON (s.id = source_id) WHERE a.type!='trashed' AND MATCH (title, description) AGAINST ('$related_phrase') AND a.id!='$articles[id]' HAVING score > 7
ORDER BY a.timestamp DESC LIMIT 0, 3");
This basically means we have a query in a loop which is causing the pages to load very slowly.
What we want to do, is bring the query from within the loop, in the main query, so it's all working within one query, if that's possible?
Any help very much appreciated!
I don't think you would gain much speed by merging the two queries.
One thing you could try is to get a list of all articles and DISTINCT searchphrases (in e.g. temptable), and then build a query to get all related articles in one single go. Lastly match up related articles with the article list.
try this:
$articles_and_related = $db->query("
SELECT *
FROM ".$prefix."articles art
LEFT JOIN (
SELECT * FROM ".$prefix."articles x
WHERE
score > 7
AND x.type != 'trashed'
AND x.id != art.id
AND MATCH(x.title, x.description) AGAINST (art.title)
LIMIT 3
) rel
LEFT JOIN ".$prefix."sources s2 ON (s2.id = rel.source_id)
LEFT JOIN ".$prefix."sources s ON (s.id = art.source_id)
WHERE
art.type!='trashed'
ORDER BY art.timestamp DESC LIMIT $start, $end");