Let's say, I have 3 tables. "users", "topics" and "replies.
The "topics" and "replies" table do have a column "user_id" which references to "id" on the "users" table. The "replies" table also have a column "topic_id" which references "id" on "topics". Also imagine that each topic has 1 reply.
Now, I want to fetch all topics and resolve the username for both tables, so the output should include a "topic_username" and a "reply_username".
I know how to select the username for the topic, but how can I do that for both the topics and replies table?
Thanks
Updated code:
SELECT
t.*,
t_users.username as topic_user,
last_reply.user_id as last_reply_user_id,
r_users.username as last_reply_username,
last_reply.replies_count,
ORDER BY IFNULL(last_reply.created_at,t.created_at DESC
FROM
topics as t
left join users as t_users on t_users.id = t.user_id
left join ( select r.*,count(r.id) as replies_count from (select * from replies order by id desc) as r group by r.topic_id ) as last_reply on last_reply.topic_id = t.id
left join users as r_users on r_users.id = last_reply.user_id
Try this
SELECT
t.*,
t_users.name as topic_user,
r_users.name as reply_user
FROM
topics as t
left join replies as r on r.topic_id=t.id
left join users as t_users on t_users.id = t.user_id
left join users as r_users on r_users.id = r.user_id
this would work well if there is 1:1 topic and reply, if you have 1 to many replies then you are better off group by topic id and get the usernames by group concat
Version 2 (to get reply count and last reply user)
SELECT
t.*,
t_users.name as topic_user,
last_reply.user_id as last_reply_user_id,
r_users.name as last_reply_username,
last_reply.replies_count,
IFNULL(last_reply.created_at,t.created_at) as last_update
FROM
topics as t
left join users as t_users on t_users.id = t.user_id
left join ( select r.*,count(r.id) as replies_count from (select * from replies order by id desc) as r group by r.topic_id ) as last_reply on last_reply.topic_id = t.id
left join users as r_users on r_users.id = last_reply.user_id
ORDER BY IFNULL(last_reply.created_at,t.created_at) DESC
You wanna do this in a single query? You can do it like this but I believe a separate query for fetching replies and topics might be better (fetch replies first, get the unique topic IDs and then fetch topics in a separate query)
SELECT r.id, r.topic_id, ru.username AS reply_username, tu.username AS topic_username
FROM replies AS r
INNER JOIN topics AS t ON (t.id = r.topic_id)
INNER JOIN users AS ru ON (r.user_id = u.id)
INNER JOIN users AS tu ON (t.user_id = u.id)
Related
I have to write a query such that ,I need to get events whose start date is of 30 min from now.
My conditions are:
1) get the event from events table
2)Join created by of events with id in users table.
3)Comments from comment table with user ser id
But the problem here is if there is no comment for event then the event it self is not coming.If any comment is present it is coming.I dont want this.If comment is not there just fetch it as empty but not hide the total event .Can anyone please help me,.Thanks.
select u.email ,group_members.user_id,users.first_name,u.first_name
as host_name,events.name,events.start_date,comments.comments,c.first_name as
comment_user,comments.id from events
inner join users as u on u.id = events.created_by
inner join comments on events.id = comments.event_id
inner join group_members on events.group_id = group_members.group_id
inner join users as c on comments.from_user = c.id
inner join users on group_members.user_id = users.id
where events.start_date between date_add(now(),interval 1 minute) and date_add(
now(),interval 30 minute)
and group_members.user_status = 2
and events.status = 2
You need a left join to the comments table. I would put that table last in the from clause.
select u.email, gm.user_id, gu.first_name, u.first_name as host_name,
e.name, e.start_date, c.comments, uc.first_name as comment_user,
c.id
from events e inner join
users u
on u.id = e.created_by inner join
group_members gm
on e.events.group_id = gm.group_id inner join
users gu
on gm.user_id = gu.id left join
comments c
on e.id = c.event_id left join
users uc
on c.from_user = uc.id
where e.start_date between date_add(now(),interval 1 minute) and date_add(now(),interval 30 minute) and
gm.user_status = 2 and
e.status = 2;
Once you use a left join on comments, you also need a left join for the from user. I replaced all table names with aliases -- this makes it easier to track which table is used for which purpose.
Use the INNER JOIN Keyword and select the two columns by putting them with keyword ON.
SELECT EMP.EMP_ID, EMP.EMP_NAME, DEPT.DEPT_NAME FROM EMP
INNER JOIN DEPT ON DEPT.DEPT_ID = EMP.DEPT_ID;
i create a web app like facebook by php and mysqli
in my app i have a table for posts , one table for likes , and one table for comments
i want to get the number of comments and likes of each post in one row with his post_id!!!
i try some querys likes this :
select `tblpost`.`post_id`, COALESCE(TCOMM.`comment_num`,0) as `c_num`, COALESCE(TLIKE.`like_num`,0) as `l_num`
from
(select `tblpost`.`post_id`, count(*) as `like_num` from `tblpost` join `tbllikes` on `tbllikes`.`post_id` = `tblpost`.`post_id` group by `tblpost`.`post_id`
) TLIKE
inner join
(select `tblpost`.`post_id`, count(*) as `comment_num` from `tblpost` join `tblcomments` on `tblcomments`.`post_id` = `tblpost`.`post_id` group by `tblpost`.`post_id`) TCOMM
on
TCOMM.`post_id` = TLIKE.`post_id`
but i don't know what's my problem
You can do count distincts with two left joins.
Something like this would work if there are fields like_id and comment_id in the tables tbllikes and tblcomments
SELECT
tblpost.post_id AS post_id,
COUNT(DISTINCT tbllikes.like_id) AS likes,
COUNT(DiSTINCT tblcomments.comment_id) AS comments
FROM tblpost
LEFT JOIN tbllikes ON tbllikes.post_id = tblpost.post_id
LEFT JOIN tblcomments on tblcomments.post_id = tblpost.post_id
GROUP BY tblpost.post_id
First, I think you can greatly simplify your query:
select l.post_id,
COALESCE(c.comment_num, 0) as c_num, COALESCE(l.like_num, 0) as l_num
from (select l.post_id, count(*) as like_num
from tbllikes l
group by l.post_id
) l inner join
(select c.post_id, count(*) as comment_num
from tblcomments c
group by c.post_id
) c
on l.post_id = c.post_id;
This will only get you posts that have both likes and comments. To get what you want, use a left join:
select p.post_id,
COALESCE(c.comment_num, 0) as c_num, COALESCE(l.like_num, 0) as l_num
from tblpost p left join
(select l.post_id, count(*) as like_num
from tbllikes l
group by l.post_id
) l
on l.post_id = p.post_id left join
(select c.post_id, count(*) as comment_num
from tblcomments c
group by c.post_id
) c
on c.post_id = p.post_id;
Okay, so I have a query below I am trying to get to work.
Basically everything works up until the inner join of the 'votes' table. What I am trying to do is order the results of this query in accordance with the number of votes each content row has in another table called votes. I know I'm not too far off from what I need to do!
Thanks in advance!!
mysql_query("
SELECT content.id, content.type, content.title, content.url, users.username
FROM content
INNER JOIN users ON content.uploaderuid = users.id
INNER JOIN votes ON votes.id = content.id
WHERE (content.type = 'pic')
ORDER BY COUNT(votes.id) DESC");
Try doing:
SELECT content.id, content.type, content.title, content.url, users.username
FROM content
INNER JOIN users ON content.uploaderuid = users.id
INNER JOIN (
SELECT id,COUNT(*) as voteCount
FROM votes
GROUP BY id
) v ON v.id = content.id
WHERE (content.type = 'pic')
ORDER BY v.voteCount DESC
When you do an INNER JOIN with votes table directly, if you have multiple occurrences of the same id, you will get a lot more rows than before you did the JOIN.
If you are only interested in the number of votes for each id, by doing a JOIN with a subquery that calculates the count of votes for each id, will leave your previous query results as they were, and lets you use the voteCount to order by it.
You could try this:
SELECT c.id, c.type, c.title, c.url, u.username, COUNT(v.id) votes
FROM content c
INNER JOIN users u ON c.uploaderuid = u.id
INNER JOIN votes v ON v.id = c.id
WHERE c.type = 'pic'
GROUP BY c.id, c.type, c.title, c.url, u.username
ORDER BY votes DESC
Here is the SQL Fiddle that demonstrates the below query:
SELECT c.id, c.type, c.title, c.url, u.username, COUNT(v.id)
FROM content AS c
INNER JOIN users AS u ON c.uploaderuid = u.id
INNER JOIN votes AS v ON v.id = c.id
WHERE c.type = 'pic'
GROUP BY c.id, c.type, c.title, c.url, u.username
ORDER BY COUNT(v.id) DESC
This can't be too hard, but I don't know what the term is I'm looking for. I'm sure you guys can help me out. :)
I have a table tasks with rows that have a column project_id. Each project_id refers to (the id of) a row in the projects table. Each project belongs to a certain user which is why it has a column user_id.
I now want to select all tasks from this table where the project_id equals any project of a certain user.
Or put more simply:
Each TASK belongs to a PROJECT which belongs to a USER.
I want to create a SELECT-statement to receive all TASKS that belong to a specific USER. The only link between each TASK and a USER is through the PROJECT.
How do I accomplish this?
Thank you very much for your help! :)
JOIN the tables:
SELECT
t.*
FROM tasks t
INNER JOIN projects p ON t.project_id = p.project_id
INNER JOIN users u ON p.user_id = u.user_id
WHERE u.user_id = #AcertianUserId
SELECT
tasks.*
FROM
users
INNER JOIN
projects ON users.id = projects.user_id
INNER JOIN
tasks ON projects.id = tasks.project_id
WHERE
users.id = 1
SQL Fiddle
select t.*
from tasks t
join projects p on p.id = t.project_id
join users u on u.id = p.user_id
where u.id = 17
Try :
SELECT t.*
FROM user u, projet p, task t
WHERE u.id = p.user_id
AND p.id = t.project_id
AND u.id = your_id
Or (same result) :
SELECT t.*
FROM user u
INNER JOIN projet p ON u.id = p.user_id
INNER JOIN task t ON p.id = t.project_id
WHERE u.id = your_id
I am trying to get the required result from the following query but it doesnt seem to work...
SELECT DISTINCT
u.user_name as user_name,
u.total_points as total_points,
u.user_id as user_id,
COUNT(a.id) as user_total_articles_published,
COUNT(r.id) as user_total_replies_published,
COUNT(v.id) as user_total_votes_done
FROM users as u
LEFT JOIN articles as a ON u.user_id=a.user_id
LEFT JOIN replies as r ON u.user_id=r.user_id
LEFT JOIN votes as v ON u.user_id=v.user_id
GROUP BY u.user_id
ORDER BY u.total_points DESC
LIMIT 10
If i remove the last 2 LEFT jOINS the query will work... whats wrong with the other 2? Do i have to use another method for this to work?
thanks
I think by 'not working' you mean that the query returns too many records? That is because of the combination of joins. You return each reply for each article record, so the numbers are multiplied. You can solve this by using DISTINCT in the COUNT. That way, you count the unique id's, so you count each article only once:
COUNT(distinct a.id) as user_total_articles_published,
COUNT(distinct r.id) as user_total_replies_published,
COUNT(distinct v.id) as user_total_votes_done
[edit]
A possibly faster solution, eliminating the need for DISTINCT and GROUP BY:
SELECT
u.user_name as user_name,
u.total_points as total_points,
u.user_id as user_id,
(SELECT COUNT(a.id) FROM articles a
WHERE a.user_id = u.user_id) as user_total_articles_published,
(SELECT COUNT(r.id) FROM replies r
WHERE r.user_id = u.user_id) as user_total_replies_published,
(SELECT COUNT(v.id) FROM votes v
WHERE v.user_id = u.user_id) as user_total_votes_done
FROM users as u
ORDER BY u.total_points DESC
LIMIT 10