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.
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 have a table which has the id column and score column, I want to sort the table based on score column and then find the specific user who is loading the page and show him his/her position. for example, tell him "your position is 40th".
Well I know how to sort a query:
SELECT id,score FROM `table` ORDER BY `score` DESC
But after the sort how can I find an specific id's position?
You don't need an order by for this. Instead:
select 1 + count(*)
from table t
where t.score > (select t2.score from table t2 where id = $id);
Try it:
SELECT #rownum:=#rownum+1 ‘rank’, id, score FROM table t, (SELECT #rownum:=0) r ORDER BY score DESC;
This will create a column and increase 1 in each record.
I have to mysql tables and trying to display results of table1 but sorting by table2. For table2 I'm counting all the occurrences of a duplicate id and then display that result descending. Below is as far as I could get and wondering if this can even be done is a single query.
$query = "
SELECT DISTINCT registration.*
FROM registration
INNER JOIN downloads
ON registration.id = downloads.id
GROUP BY downloads.COUNT(id)
ORDER BY downloads.COUNT(id) DESC,
downloads.COUNT(id) DESC
";
I think you want something along these lines:
SELECT Registration.id, Registration.name, Registration.email,
Downloads.document
FROM Registration
JOIN Downloads
ON Downloads.id = Registration.id
JOIN (SELECT id, COUNT(*) as count
FROM Downloads
GROUP BY id) Download_Count
ON Download_Count.id = Registration.id
ORDER BY Download_Count.count DESC
(untested, as it would be nice for the OP to supply sample data and table layouts in the question)
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
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