I have this diagram
What I wanna do is have this output:
How do you manage to do the query of this one?
I have this code
SELECT users.firstname, users.lastname,
users.screenname, posts.post_id, posts.user_id,
posts.post, posts.upload_name,
posts.post_type, posts.date_posted
FROM website.users users
INNER JOIN website.posts posts ON (users.user_id = posts.user_id)
ORDER BY posts.pid DESC
//PROBLEM with this one is that it only views the post from all users.
//SO I added
SELECT COUNT(user_id) AS friends, SUM(user_id = ?) AS you, user_id
FROM feeds WHERE post_id = ?
//This one will give you two fields containing how many different users **feeds** the
post
Please help guys. Actually this one I am just following Facebook's "LIKE" status
the only thing is I'm not an amateur with this kind of stuff so I'd be glad to hear all your answers. I really need your help
If I've understood you correctly, you want an outer join with the feeds table (in order to retain all posts even if there are no associated feeds), then GROUP BY post.pid in order to amalgamate together all such feeds for each post, and SELECT the desired information.
I use MySQL's GROUP_CONCAT() function to obtain a comma-separated list of all users (up to group_concat_max_len) who have
a "feed" for the given post (you can change the delimiter with the SEPARATOR modifier, if so desired).
SELECT users.firstname, users.lastname,
users.screenname, posts.post_id, posts.user_id,
posts.post, posts.upload_name,
posts.post_type, posts.date_posted,
COUNT(feeds.user_id) AS friends, -- number of "likes"
SUM(feeds.user_id = ?) AS you, -- did I like this?
GROUP_CONCAT(feeds.user_id) -- who likes it?
FROM website.users users
INNER JOIN website.posts posts ON (users.user_id = posts.user_id)
LEFT JOIN website.feeds feeds ON (posts.post_id = feeds.post_id)
GROUP BY posts.pid
ORDER BY posts.pid DESC
UPDATE
To obtain the full name of users who have "liked" the post, excluding oneself, one needs to join the users table a second time:
SELECT users.firstname, users.lastname,
users.screenname, posts.post_id, posts.user_id,
posts.post, posts.upload_name,
posts.post_type, posts.date_posted,
COUNT(feeds.user_id) AS friends, -- number of "likes"
SUM(feeds.user_id = ?) AS you, -- did I like this?
GROUP_CONCAT(
CASE WHEN NOT likes.user_id = ? THEN -- exclude self
CONCAT_WS(' ', likes.firstname, likes.lastname) -- full names
END
)
FROM website.users users
INNER JOIN website.posts posts ON (users.user_id = posts.user_id)
LEFT JOIN website.feeds feeds ON (posts.post_id = feeds.post_id)
LEFT JOIN website.users likes ON (feeds.user_id = likes.user_id)
GROUP BY posts.pid
ORDER BY posts.pid DESC
If You want to do it for all the users and simultaneously get the feeds, You have to join this feed table:
SELECT u.firstname, u.lastname,
u.screenname, p.post_id, p.user_id,
p.post, p.upload_name,
p.post_type, p.date_posted,
COUNT(f.user_id) AS friends, SUM(f.user_id = ?) AS you
FROM website.users u
INNER JOIN website.posts p ON (u.user_id = p.user_id)
LEFT JOIN website.feeds f ON (p.post_id = f.post_id)
GROUP BY p.pid
ORDER BY p.pid DESC
This one should do the trick...
Related
I am working on an sql query where I have three tables posts, users and comments. I want to display all posts with its users and number of comments on this. I have following query but it is giving me wrong result:
SELECT
c.userid, count(c.userid), p.postid
FROM comments c, posts p
where c.userid = p.userid group by c.userid
In addition to above query I also require firstname and lastname from users table.
Try something like this,
SELECT
u.userid, u.firstname, u.lastname,p.post, p.postid,
count(c.userid) totalcoments -- may be c.commentid
FROM users u
JOIN posts p ON p.userid=u.userid
LEFT JOIN comments c OM c.postid=p.postid
GROUP BY u.userid, u.firstname, u.lastname,p.post, p.postid
Try something like the following:
SELECT
postid
, p.userid
, COALESCE((
SELECT COUNT( * ) FROM comments WHERE postid = p.id
), 0 ) AS cnt_postid
, COALESCE( ( SELECT CONCAT( firstname, ' ', lastname ) FROM users WHERE userid = p.userid ), 'N/A' ) AS NAME
FROM posts p
LEFT JOIN comments c ON c.postid = p.id
GROUP BY postid
ORDER BY postid
you are probably getting the same amount of count because you not using a group by.
GROUP BY must always be used when using aggregate function. What the group by does is that it will select all unique posts and the the count will return the number of users for that one unique post
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)
I have a projects table and a tasks table I want to do a query that gets all projects and the sum of the time_spent columns grouped by project id. So essentially list all projects and get the total of all the time_spent columns in the tasks table belonging to that project.
With the query posted below I get the latest added time_spent column and not the sum of all the columns.. :S
Below is the query I have at the moment:
SELECT `projects`.`id`, `projects`.`description`, `projects`.`created`,
`users`.`title`, `users`.`firstname`, `users`.`lastname`, `users2`.`title`
as assignee_title, `users2`.`firstname` as assignee_firstname,
`users2`.`lastname` as assignee_lastname,
(select sum(tasks2.time_spent)
from tasks tasks2
where tasks2.id = tasks.id)
as project_duration
FROM (`projects`)
LEFT JOIN `users`
ON `users`.`id` = `projects`.`user_id`
LEFT JOIN `users` as users2
ON `users2`.`id` = `projects`.`assignee_id`
LEFT JOIN `tasks` ON `tasks`.`project_id` = `projects`.`id`
GROUP BY `projects`.`id`
ORDER BY `projects`.`created` DESC
Below is my projects table:
Below is my tasks table:
Thanks in advance!
Usually this query will help you.
SELECT p.*, (SELECT SUM(t.time_spent) FROM tasks as t WHERE t.project_id = p.id) as project_fulltime FROM projects as p
In your question, you don't say about users. Do you need users?
You are on right way, maybe your JOINs can't fetch all data.
This query should do it for you.
Note, whenever you do a group by you must include every column that you select from or order by. Some MySql installations don't prevent you from doing this, but in the end it results in an incorrect result set.
As well you should never do a query as part of your SELECT statement, known as a sub-query, as it will result in an equal amount of additional queries in relation to the number of rows returned. So if you got 1,000 rows back, it would result in 1,001 queries instead of 1 query.
SELECT
p.id,
p.description,
p.created,
u.title,
u.firstname,
u.lastname,
a.title assignee_title,
a.firstname assignee_firstname,
a.lastname assignee_lastname,
SUM(t.time_spent) project_duration
FROM
projects p
LEFT JOIN
users u ON
u.id = p.user_id
LEFT JOIN
users a ON
a.id = u.assignee_id
LEFT JOIN
tasks t ON
t.project_id = p.id
GROUP BY
p.id,
p.description,
p.created,
u.title,
u.firstname,
u.lastname,
a.title,
a.firstname,
a.lastname
ORDER BY
p.created DESC
This is my query:
SELECT messages.id AS m_id, messages.user_id AS m_uid, messages.project_id AS m_pid, messages.date_created AS m_dc, messages.type AS m_type, messages.file_url AS m_fu, messages.message_text AS m_text, messages.deleted AS m_del,
projects.id AS p_id, projects.name AS p_name, projects.company_id AS p_cid,
users.id AS u_id, users.name AS u_name
FROM messages, projects, users
HAVING `m_pid` = '$project_id' AND m_uid = u_id
ORDER BY `m_dc` DESC
I've been using HAVING instead of WHERE because WHERE doesn't seem to be working with the AS keywords I'm using. The result is that my query is returning more results than I need. I think I'm supposed to be using JOINs here, but I can't really get a grasp on them. Please help!
:) Thanks
It's true, you should use JOIN instead of the FROM table1, table2 syntax.
To answer your issue more directly: the WHERE clause operates on the columns in the tables - the HAVING clause operates on your result set (which includes your aliases).
How do your tables relate to each other? That is the question you need to answer first - once you have that answer, you put it pretty much directly into the ON clause of the JOIN.
SELECT messages.id AS m_id, messages.user_id AS m_uid, messages.project_id AS m_pid, messages.date_created AS m_dc, messages.type AS m_type, messages.file_url AS m_fu, messages.message_text AS m_text, messages.deleted AS m_del, projects.id AS p_id, projects.name AS p_name, projects.company_id AS p_cid,
users.id AS u_id, users.name AS u_name
FROM messages
JOIN users ON messages.user_id = user.id
JOIN projects ON projects.user_id = user.id # this is just a guess
WHERE messages.id = $project_id
ORDER BY `m_dc` DESC
To get a better idea of how JOINs relate tables together, you might want to check out this handy page showing JOINs as Venn diagrams.
SELECT
messages.id AS m_id, messages.user_id AS m_uid, messages.project_id AS m_pid,
messages.date_created AS m_dc, messages.type AS m_type, messages.file_url AS m_fu,
messages.message_text AS m_text, messages.deleted AS m_del,
projects.id AS p_id, projects.name AS p_name, projects.company_id AS p_cid,
users.id AS u_id, users.name AS u_name
FROM
messages
JOIN
users ON messages.user_id = users.id
JOIN
projects ON projects.id=messages.project_id
WHERE
`m_pid` = '$project_id'
ORDER BY
`m_dc` DESC
Try this?
SELECT m.id AS m_id,
m.user_id AS m_uid,
m.project_id AS m_pid,
m.date_created AS m_dc,
m.type AS m_type,
m.file_url AS m_fu,
m.message_text AS m_text,
m.deleted AS m_del,
p.id AS p_id,
p.name AS p_name,
p.company_id AS p_cid,
u.id AS u_id,
u.name AS u_name
FROM messages as m
INNER JOIN projects as p on p.id = m.project_id
INNER JOIN users as u ON u.id = m.user_id
WHERE m.project_id = '$project_id'
ORDER BY ....
I have two tables called 'events' and 'topics' each table can have many comments.
What I need to do is list all the events and topics with the amount of comments for each row. I've managed to return all the topics, which works great but I don't know how I can add the events table to the MySql. The comments and events table fields are listed below. Can anyone help me with this query?
Events:
ID
Event_Name
Comments:
post_id <-- the releated id for either the events or topics table
table <-- The table that the row belongs to so either topics or events
SELECT
t.id, t.title, c.created_at,
IF(ISNULL(c.allComments), 0, c.allComments) AS totalComments
FROM topics AS t
LEFT OUTER JOIN (
SELECT created_at, post_id, COUNT(*) AS allComments
FROM comments
GROUP BY post_id
) AS c ON c.post_id = t.id
ORDER BY tc.created_at DESC, c.allComments DESC
Sounds like events and topics should be the same table.
Still, I think we can do this with a UNION. Events and Topics have the same columns i hope? (Or at least the same important ones?)
(SELECT c.table as event_or_topic, e.*, count(C.table), MAX(C.created_at) as latest_c
FROM events E LEFT JOIN comments C on (C.post_id = E.id)
WHERE C.table = 'Events'
GROUP BY C.post_id)
UNION
(SELECT c.table as event_or_topic, t.id*, count(C.table), MAX(C.created_at) as latest_c
FROM topics T LEFT JOIN comments C on (C.post_id = E.id)
WHERE C.table = 'Topics'
GROUP BY C.post_id)
ORDER BY latest_c
Notice that the ORDER BY applies to the whole UNION, not the individual SELECTs.
The use of LEFT JOIN should allow those rows without Comments to still show. I think the problem is that we have parts of our select dependent on comments (ie - C.table, ordering on last comment, etc). The count should be fine - will just be zero if there are no comments.
You might need to change the SELECT part slightly. I'd like to display C.table so you know whether a row is a topic or event, but im afraid it might screw up the count. Do you need anything from comments besides the count? You use some columns other than post_id and table in your query that you neglected to explain in your question.
You still have columns I don't know what they are, like Comment's zoneTable
Try this:
SELECT
t.id, t.title, c.created_at, COUNT(c.allComments) AS totalComments
FROM topics AS t LEFT JOIN comments c ON t.id=c.post_id
GROUP BY t.id ORDER BY tc.created_at DESC, c.allComments DESC
If I understand your question you have 3 tables:
-Events
-Topics
-Comments
If that is true something like this should extract all the data:
SELECT *
FROM events,topics
LEFT JOIN comments ON post_ID = ID
ORDER BY date DESC
Hope i'm along the right lines!
W.
I've got it working. If anyone knows of a better and an efficient way of doing this, then please let me know:
(SELECT t.id, t.title, tc.dateCreated AS commentDate,
IF(ISNULL(tc.allComments), 0, tc.allComments) AS totalComments,
t.LastActive as dateChanged
FROM Events AS t
LEFT OUTER JOIN (
SELECT MAX(created_at) AS dateCreated, post_id,
COUNT(*) AS allComments
FROM comments
GROUP BY post_id
) AS tc ON tc.post_id = t.id)
UNION
(SELECT t.id, t.title, tc.dateCreated AS commentDate,
IF(ISNULL(tc.allComments), 0, tc.allComments) AS totalComments,
t.LastActive as dateChanged
FROM topics AS t
LEFT OUTER JOIN (
SELECT MAX(created_at) AS dateCreated, post_id,
COUNT(*) AS allComments
FROM comments
GROUP BY post_id
) AS tc ON tc.post_id = t.id)
ORDER BY commentDate DESC, dateChanged DESC, totalComments DESC