I have a select to get alerts.
select 'comments' prefix, c.foto, c.data as data, c.user, concat(k.user, ' comments your post') as logs from comentarios c
inner join posts p on c.foto = p.id
inner join cadastro k on c.user = k.id
where p.user = 1 and p.user <> c.user and c.delete = 0
union all
select 'like' prefix, l.post, l.data as data, l.user, concat(k.user, ' liked your post') as logs from likes l
inner join posts p on l.post = p.id
inner join cadastro k on l.user = k.id
where p.user = 1 and l.user <> p.user
order by data desc
limit 5
The problem is if I run the select this way it will take 2.4871 seconds.
If I remove the select 'like'... = 0.0024, but if I run this select apart it will take only 0.010 without the order by data desc.
any ideas why? I don't know if the problem is the union or the order by...
they are all well indexed.
How do i limit inner join to 1 with order by DESC on this part
INNER JOIN comments ON thread.t=comments.comment_id
this is my code https://gist.github.com/anonymous/cf7de8400327b98631d2f6d9b23084b5
look at result output there is the problem on duplicate content because of comments (need to limit 1) #M Khalid Junaid
Do a self join to your comments table to pick the recent comment only for each post
SELECT
t.t_dp,
t.t,
t.t_id,
t.tittle,
t.t_username,
t.t_date_posting,
t.views,
c.comments,
c.comment_time,
c.comment_id,
c.c
FROM
thread t
INNER JOIN comments c
ON t.t = c.comment_id
LEFT JOIN comments c1
ON c.comment_id = c1.comment_id
AND c.id < c1.id
WHERE t.t_type = '02'
AND c1.id IS NULL
LIMIT #start_from, #results_per_page
Also you are using LIMIT without ORDER BY which makes no sense, In which order limit applies on records.
I have this structure in MySql
I am trying to get:
FIRST post, from LAST topic WHERE category is 'News'
In this example it is row from post where id = 2 as marked on image
So far I got this query:
SELECT *
FROM forum_post AS p
LEFT JOIN forum_topic AS t ON p.topic_id = t.id
LEFT JOIN forum_category AS c ON t.category_id = c.id
WHERE c.title = 'News' AND t.id = MAX(t.id)
ORDER BY p.id ASC LIMIT 1
EDIT:
Dirty solution:
SELECT * FROM forum_post
WHERE topic_id = (SELECT MAX(id) FROM forum_topic WHERE category_id = 1)
ORDER BY id ASC LIMIT 1
You can still use a joined query instead of a subquery to get the first post from last topic of your category,note the subquery in join will run only once to get the result set and in your case subquery will run for each iteration
SELECT * FROM
forum_post AS p
JOIN
(SELECT
t.id
FROM
forum_topic AS t
JOIN forum_category AS c
ON t.category_id = c.id
WHERE c.title = 'News'
ORDER BY t.id DESC
LIMIT 1) t
ON p.topic_id = t.id
ORDER BY p.id ASC
LIMIT 1
select fp.* from forum_post fp,
(select min(fp.id) from forum_post fp where topic_id in
(select max(ft.id) from forum_topic ft inner join forum_category fc
on fc.id = ft.category_id where fc.title = 'News'))T
where fp.id = T.id
[In case there are no forum_posts, no row will be returned]
Edit:
Updated [Although I haven't tried executing it]
I haven't test it, but it shoud be something like this:
SELECT fm.remply
FROM forum_topic ft
JOIN forum_category fc
ON ft.category_id = fc.category_id
AND fc.title = 'News'
JOIN forum_post fm
ON ft.id = fm.topic_id
ORDER BY ft.id DESC
,fm.id DESC
LIMIT 1
I have a MySQL query that is currently using a nested select, and I am wondering if it is possible to rewrite the query to not use a nested select, and if so how?
The query is as follows
SELECT
b.id,
b.name,
b.description,
b.order,
b.icon,
b.locked,
u.username AS lastPoster,
p.time AS lastPostTime,
p1.subject AS lastPostTopicSubject,
p2.postscount AS totalPosts,
t1.topicscount AS totalTopics,
p.subject AS lastPostSubject,
t.id AS lastPostTopicId
FROM kf_boards AS b
LEFT JOIN kf_topics AS t ON (t.boardid = b.id)
LEFT JOIN (SELECT posterid, topicid, time, subject
FROM kf_posts
ORDER BY time DESC) AS p ON (p.topicid = t.id)
LEFT JOIN (SELECT subject
FROM kf_posts
ORDER BY time ASC) AS p1 ON (p.topicid = t.id)
LEFT JOIN (SELECT COUNT(id) AS postscount
FROM kf_posts) AS p2 ON (p.topicid = t.id)
LEFT JOIN (SELECT COUNT(id) AS topicscount
FROM kf_topics) AS t1 ON (t.boardid = b.id)
LEFT JOIN kf_users AS u ON (p.posterid = u.id)
WHERE b.categoryid = :catid
GROUP BY b.name
ORDER BY b.order
And the database structure is as follows
Any help would be much appriciated!
Thanks!
Edit: Tried below query, results returned
Results should be as follows
try:
SELECT
b.id, b.name, b.description, b.order, b.icon, b.locked,
u.username AS lastPoster, p.time AS lastPostTime,
p.subject AS lastPostSubject, t.id AS lastPostTopicId
FROM kf_boards AS b
LEFT JOIN kf_topics AS t ON t.boardid = b.id
LEFT JOIN kf_posts AS p ON p.topicid = t.id
LEFT JOIN kf_users AS u ON p.posterid = u.id
WHERE b.categoryid = :catid
GROUP BY b.name
ORDER BY b.order ASC, p.time DESC
UPDATE: bellow is for your new query.
SELECT b.id, b.name, b.description, b.order, b.icon, b.locked,
u.username AS lastPoster, MAX(p.time) AS lastPostTime,
p.subject AS lastPostTopicSubject, count(p.id) AS totalPosts,
count(t.id) AS totalTopics, p.subject AS lastPostSubject,
max(t.id) AS lastPostTopicId
FROM kf_boards AS b
LEFT JOIN kf_topics AS t ON t.boardid = b.id
LEFT JOIN kf_posts AS p ON p.topicid = t.id
LEFT JOIN kf_users AS u ON p.posterid = u.id
WHERE b.categoryid = :catid
GROUP BY b.name, b.id, b.name, b.description, b.order, b.icon,
b.locked, u.username, p.subject
ORDER BY b.order
Here's a solution that might help, however, I have additional suggestions to simplify all querying later via triggers. I'll explain that later.
I'm starting with the inner-most query on just board IDs for category (your parameter) and that the board HAS POSTINGS (not via LEFT-JOIN). From this, I am getting just the maximum post ID per board regardless of topic (just that it must be of a valid board per the joins).
Once I have that, the next query out re-joins to the posts table based on the last post to determine the topic... then re-joins THAT to the posts again on the same topic ID. With that, I can get the FIRST Post ID and total Entries for this topic for the board... all grouped per "board ID".
These are obviously only boards that HAVE AT LEAST 1 Board, but that's not what you want. You want ALL boards regardless of a post. So, I'm back to the beginning to query kf_boards again with same WHERE on category ID = your parameter... THIS gets you all the boards for the category...
NOW, you can left-join to the pre-aggregate query for min/max post and entries count... Then take THAT to left-join to the posts table again but TWICE... Once for the FIRST post (so you can get the initial subject caption, time and whatever else you might care about), and AGAIN for the LAST POST to get ITs time, subject, etc... You already have the total post entries for this topic from the pre-aggregate query. Finally, a left-join on the last post to the users table to see who posted it last.
I've tested the syntax on it and it works, just can't confirm based on actual data.
SELECT
B.ID,
B.Name,
B.Description,
B.Order,
B.Icon,
FP.Subject as FirstPostSubject,
FP.Time as FirstPostTime,
LP.Subject as LastPostSubject,
LP.Time as LastPostTime,
U.UserName as LastPostUserName,
QryPerBoard.PostEntries
from
kf_boards B
LEFT JOIN
( select
PQ1.ID,
PQ1.LastPostID,
MIN( P2.ID ) as FirstPostID,
COUNT(*) as PostEntries
from
( SELECT
B1.ID,
MAX( P1.ID ) as LastPostID
from
kf_boards B1
join kf_topics T1
ON B1.ID = T1.BoardID
join kf_posts P1
ON T1.ID = P1.TopicID
where
B1.CategoryID = 1 <-- Insert your Category Parameter ID here
group by
B1.ID ) as PQ1
LEFT JOIN kf_posts P1
ON PQ1.LastPostID = P1.ID
LEFT JOIN kf_posts P2
ON P1.TopicID = P2.TopicID
group by
PQ1.ID ) QryPerBoard
ON B.ID = QryPerBoard.ID
LEFT JOIN kf_posts FP
ON QryPerBoard.FirstPostID = FP.ID
LEFT JOIN kf_posts LP
ON QryPerBoard.LastPostID = LP.ID
LEFT JOIN kf_users U
ON LP.PosterID = U.ID
where
B.CategoryID = 1 <-- Insert your Category Parameter ID here (second copy for parameter)
Now, how I would adjust to prevent the recursive level of querying, especially for a website. Use triggers. When a POST is created and saved, have a trigger that does a few things...
REVISED THOUGHT on trigger impact.
Update the kf_Boards with the latest TOPIC ID any post was created for the respective board ID so you never have to look for it later, just take whatever is the last and run with it. In addition, update the TOPIC record. Have a column for the FIRST POST, LAST POST and TOTAL POSTS for the topic. If its the first post to the topic, update both first AND last post with the new ID and increment the total post count.
The time to incorporate these triggers to update the "extra" columns would save such complexities for future queries. You'll basically be able to do something like
select
B.*,
LP.Fields, <obviously apply specific fields you want per table>
FP.Fields,
U.Fields
from
kf_boards B
LEFT JOIN kf_topics T
on B.LastTopicID = T.ID
LEFT JOIN kf_posts FP
on T.FirstPostID = FP.ID
LEFT JOIN kf_posts LP
on T.LastPostID = LP.ID
LEFT JOIN kf_users U
on LP.PosterID = U.ID
where
B.CategoryID = 1 <-- your parameterID
It seems possible to remove all the subqueries,
but the query will be more clear if the last post, and the first post on the corresponding
topic is found using subqueries:
SELECT b.id, b.name, b.description, b.sortorder, b.icon, b.locked,
u.username AS lastPoster,
p1.time AS lastpostTime,
p0.subject AS lastPostTopicSubject,
COUNT(DISTINCT p.id) AS totalPosts,
COUNT(DISTINCT t.id) AS totalTopics,
p1.subject AS lastPostSubject,
p1.topicid AS lastPostTopicId
FROM kf_boards b
LEFT JOIN kf_topics t ON t.boardid = b.id
LEFT JOIN kf_posts p ON p.topicid = t.id
LEFT JOIN kf_posts p1
ON p1.time = (SELECT MAX(time) FROM kf_posts p
INNER JOIN kf_topics t
ON p.topicid = t.id
WHERE t.boardid = b.id)
LEFT JOIN kf_users u ON u.id = p1.posterid
LEFT JOIN kf_posts p0
ON p0.time = (SELECT MIN(time) FROM kf_posts p0
WHERE p0.topicid = p1.topicid)
WHERE b.categoryid = :catid
GROUP BY b.id
ORDER BY b.sortorder;
However, the following query, using self joins to find posts that have no related previous/nest post should give the same answer:
SELECT b.id, b.name, b.description, b.sortorder, b.icon, b.locked,
u.username AS lastPoster,
lastpost.time AS lastpostTime,
firstpost.subject AS lastPostTopicSubject,
COUNT(DISTINCT p.id) AS totalPosts,
COUNT(DISTINCT t.id) AS totalTopics,
lastpost.subject AS lastPostSubject,
lastpost.topicid AS lastPostTopicId
FROM kf_boards b
LEFT JOIN kf_topics t ON t.boardid = b.id
LEFT JOIN kf_posts p ON p.topicid = t.id
LEFT JOIN kf_topics lasttopic ON lasttopic.boardid = b.id
LEFT JOIN kf_posts lastpost ON lastpost.topicid = lasttopic.id
LEFT JOIN kf_topics nexttopic ON nexttopic.boardid = b.id
LEFT JOIN kf_posts nextpost -- order posts
ON nextpost.topicid = nexttopic.id -- in same board
AND nextpost.time > lastpost.time -- by time
LEFT JOIN kf_users u ON u.id = lastpost.posterid
LEFT JOIN kf_posts AS firstpost ON firstpost.topicid = lastpost.topicid
LEFT JOIN kf_posts prevpost -- order posts
ON prevpost.topicid = firstpost.topicid -- on same topic
AND prevpost.time < firstpost.time -- by time
WHERE nextpost.id IS NULL -- last post has no next
AND prevpost.id IS NULL -- first post on topic has no previous
AND b.categoryid = :catid
GROUP BY b.id
ORDER BY b.sortorder;
Check the result at http://sqlfiddle.com/#!2/1c042/1/0
$query = $this->db->query("SELECT a.fullname AS fullname_post , a.picture, a.user_id, c.post_id, c.date_posted, c.total_comments, c.content AS post, UNIX_TIMESTAMP() - c.date_posted AS p_time_spent, c.photo, d.comment_id, d.comment_date, d.content AS comments, UNIX_TIMESTAMP() - d.comment_date AS c_time_spent, d.post_id_fk, e.fullname AS fullname_comments
from $post_table c
LEFT JOIN $comments_table d ON d.post_id_fk = c.post_id
LEFT JOIN $user_table a on a.user_id=c.post_owner_fk
LEFT JOIN $user_table e on e.user_id=d.comment_owner_id_fk
LEFT JOIN $contact_table f on f.user_id_fk='$user_id' OR f.user_id_fk2='$user_id'
WHERE c.post_owner_fk = '$user_id' OR c.post_owner_fk = f.friend_id_fk OR c.post_owner_fk = f.friend_id_fk2
ORDER BY c.post_id DESC, d.comment_id ASC"
);
The mysql query above works fine if I just want to retrieve all comments to a specific post but I have no idea how to limit the number of comments to display.
I try to put select in one of the left join and put some limit.
LEFT JOIN (SELECT * FROM $comments_table LIMIT 4) d ON d.post_id_fk = c.post_id
but it only display 4 comments and the other posts has no comments displayed even if there are comments in the database. I think it only retrieve 4 comments in the comment table.
So please any idea how to solve this problem thanks!
Can you try something like this in MySQL?
SELECT a.fullname AS fullname_post , a.picture, a.user_id, c.post_id, c.date_posted,
c.total_comments, c.content AS post, UNIX_TIMESTAMP() - c.date_posted AS p_time_spent,
c.photo, d.comment_id, d.comment_date, d.content AS comments,
UNIX_TIMESTAMP() - d.comment_date AS c_time_spent, d.post_id_fk,
e.fullname AS fullname_comments
FROM $post_table c
LEFT JOIN $comments_table d ON d.post_id_fk = c.post_id
LEFT JOIN
(SELECT tmpc.post_id_fk
FROM $comments_table tmpc
WHERE tmpc.post_id_fk = c.post_id
ORDER BY tmpc.comment_date DESC
LIMIT 4) as climited
ON climited.post_id_fk = c.post_id
LEFT JOIN $user_table a on a.user_id=c.post_owner_fk
LEFT JOIN $user_table e on e.user_id=d.comment_owner_id_fk
LEFT JOIN $contact_table f on f.user_id_fk='$user_id'
OR f.user_id_fk2='$user_id'
WHERE c.post_owner_fk = '$user_id'
OR c.post_owner_fk = f.friend_id_fk
OR c.post_owner_fk = f.friend_id_fk2
ORDER BY c.post_id DESC, d.comment_id ASC
Edit:
Replaced the IN clause with another join to a 'limited' SELECT query