How do I unite these two?
This query:
SELECT f1.asked_user_id AS friend_id
FROM friends AS f1 JOIN friends AS f2
ON f1.asked_user_id = f2.asker_user_id
AND f1.asker_user_id = f2.asked_user_id
AND f1.asker_user_id = :user_id
WHERE f1.status = 1 AND f2.status = 1
With:
(SELECT GROUP_CONCAT(words_en.word) FROM connections JOIN words_en ON connections.word_id = words_en.id WHERE connections.user_id = friends.friend_id) As friend_words
And do yet another join:
JOIN users ON friends.friend_id = users.id
I've tried few things here: http://www.sqlfiddle.com/#!2/85d6d/36
First query selects two way friends from the table. I get friend_id from that query.
Now I want to know more about this friend_id.
So I want to use this id to do another query that would display all word_ids from connections table by that user, word_ids can be used to get actual words from words_en.
And lastly, I want to get users name_surname from users table.
Try this:
SELECT a.name_surname,GROUP_CONCAT(Distinct w.word Order by w.word asc) AS words
FROM (
SELECT f1.asked_user_id AS friend_id,
f1.created,
u.name_surname,
u.avatar
FROM friends AS f1
INNER JOIN friends AS f2 ON f1.asked_user_id = f2.asker_user_id
INNER JOIN users AS u ON f1.asked_user_id = u.id
AND f1.asker_user_id = f2.asked_user_id
AND f1.asker_user_id = 1
WHERE f1.status = 1 AND f2.status = 1
) a
LEFT JOIN connections c ON c.user_id = a.friend_id
LEFT JOIN words_en w ON c.word_id = w.id
GROUP BY 1;
sqlfiddle demo
Having your original query, what i did is treat that query as a table (a) and LEFT JOIN it with connections table. Then, LEFT JOIN the connections table with the words_en table to reach the desired words. This makes it possible to get all users that return from your original query, even when there are no connections/words.
Related
This query is taking forever to finish in MySql 8, doing some research i found out that the "EXISTS" in this code can be extremely slow in some queries.
When i remove the "OR EXISTS" sub-query part, it runs in less than a second.
So i need to substitute the "OR EXISTS" in this query so i can get all the users i need:
SELECT u.name,
u.email,
u.cpf,
u.register,
r.name AS role_name,
s.name AS sector_name,
b.name AS branch_name,
u.status
FROM users u
INNER JOIN roles r ON r.id = u.role_id
INNER JOIN sectors s ON s.id = u.sector_id
INNER JOIN branches b ON b.id = u.branch_id
WHERE u.status = 2 OR EXISTS (
SELECT *
FROM user_recovery ur
WHERE ur.user_id = u.id
AND ur.status_recovery = 1
)
Is there a way to do it without the "OR EXISTS"?
Or can enforce a full scan
try
you can't get rid of the eXISTS clause because it increases the number of returned rows.
Add a INDEX on user status and user_recovery userid,status_recovery and on the on Clause columns.
SELECT u.name,
u.email,
u.cpf,
u.register,
r.name AS role_name,
s.name AS sector_name,
b.name AS branch_name,
u.status
FROM users u
INNER JOIN roles r ON r.id = u.role_id
INNER JOIN sectors s ON s.id = u.sector_id
INNER JOIN branches b ON b.id = u.branch_id
WHERE u.status = 2
UNION
SELECT u.name,
u.email,
u.cpf,
u.register,
r.name AS role_name,
s.name AS sector_name,
b.name AS branch_name,
u.status
FROM users u
INNER JOIN roles r ON r.id = u.role_id
INNER JOIN sectors s ON s.id = u.sector_id
INNER JOIN branches b ON b.id = u.branch_id
WHERE EXISTS (
SELECT 1
FROM user_recovery ur
WHERE ur.user_id = u.id
AND ur.status_recovery = 1
)
"I'll see your UNION; and raise you a derived table."
SELECT u.name,
u.email,
u.cpf,
u.register,
r.name AS role_name,
s.name AS sector_name,
b.name AS branch_name,
u.status
FROM ( SELECT id
FROM users
WHERE status = 2
UNION DISTINCT -- or UNION ALL; see below
SELECT user_id
FROM user_recovery
WHERE status_recovery = 1 -- see new index
) AS u1
JOIN users AS u USING(id) -- self-join to pick up other columns
JOIN roles r ON r.id = u.role_id
JOIN sectors s ON s.id = u.sector_id
JOIN branches b ON b.id = u.branch_id;
Indexes:
user_recovery: INDEX(status_recovery, user_id) -- in this order
users: INDEX(status, id) -- in this order
(I assume `id` is the PRIMARY KEY in each table)
The general rule here is... When you have a bunch of JOINs, but a single table that controls which rows, but that is messy or slow (eg UNION in this case, GROUP BY or LIMIT in other cases),
Optimize finding the ids (user.id aka user_id) is the optimal way.
Then JOIN back to the original table (if needed), plus the other tables.
In doing all that, it became apparent that a new index for user_recovery might be beneficial.
(If UNION ALL won't produce any dups, switch to it for a little more speed.)
I have 3 tables users, user_group, and groups.
users have one to many relationship with groups.
If I want to fetch only those users who don't have group Mathematics.
I have using the following query for this purpose:
SELECT * FROM users
INNER JOIN user_group ON user_group.user_id = user.UserID
INNER JOIN groups ON user_group.group_id = groups.group_id
WHERE groups.Name <> 'Mathematics';
But it is returning multiple records against all Users. Suppose, if I have user John and he joined 3 groups Science, Mathematics and English. In this case, it will return two records of user John. I want to remove user John totally from the list.
You can use NOT EXISTS:
SELECT *
FROM users AS u
WHERE NOT EXISTS (SELECT 1
FROM user_group AS ug
INNER JOIN groups AS g ON ug.group_id = g.group_id
WHERE ug.user_id = u.UserID AND g.Name = 'Mathematics');
Demo here
If you want to do it using joins, then this is a way:
SELECT u.*
FROM users AS u
LEFT JOIN (
SELECT user_id
FROM user_group
INNER JOIN groups
ON user_group.group_id = groups.group_id AND groups.Name = 'Mathematics'
) AS g ON u.UserID = g.user_id
WHERE g.user_id IS NULL
Demo here
SELECT * FROM users
LEFT JOIN user_group ON user.UserID = user_group.user_id
LEFT JOIN groups ON user_group.group_id = groups.group_id
WHERE groups.Name != 'Mathematics';
To get pending request for selected user I use:
SELECT f1.asker_user_id AS friend_id
FROM friends AS f1
LEFT JOIN friends AS f2
ON f1.asked_user_id = f2.asker_user_id
AND f1.asker_user_id = f2.asked_user_id
WHERE f1.status = 1 AND f2.status IS NULL
AND f1.asked_user_id = 2
http://www.sqlfiddle.com/#!2/0f7a0d5/65 It correctly returns user 3. VALUES (3,2,1)
But I'd like to get more data about this user 3.
I need name_surname and avatar from users table.
And all word_ids of this user from connections table, which in return would show word from words_en based on word_id.
Thanks allot!
p.s. I tried this:
SELECT a.name_surname,GROUP_CONCAT(Distinct w.word Order by w.word asc) AS words
FROM (
SELECT f1.asked_user_id AS friend_id,
f1.created,
u.name_surname,
u.avatar
FROM friends AS f1
LEFT JOIN friends AS f2 ON f1.asked_user_id = f2.asker_user_id
INNER JOIN users AS u ON f1.asked_user_id = u.id
AND f1.asker_user_id = f2.asked_user_id
WHERE f1.status = 1 AND f2.status IS NULL
AND f1.asker_user_id = 2
) a
LEFT JOIN connections c ON c.user_id = a.friend_id
LEFT JOIN words_en w ON c.word_id = w.id
GROUP BY 1;
Based on this question and your previous questions, i think you might be looking for something like this:
SELECT u.name_surname,
u.avatar,
GROUP_CONCAT(DISTINCT w.word Order by w.word asc) AS words
FROM users u
INNER JOIN
(
SELECT f1.asker_user_id AS friend_id
FROM friends AS f1
LEFT JOIN friends AS f2
ON f1.asked_user_id = f2.asker_user_id
AND f1.asker_user_id = f2.asked_user_id
WHERE f1.status = 1 AND f2.status IS NULL
AND f1.asked_user_id = 2
) a ON a.friend_id = u.id
LEFT JOIN connections c ON u.id = c.user_id
LEFT JOIN words_en w ON w.id = c.word_id
GROUP BY u.id;
sqlfiddle demo
HERE IS THE SQL Fiddle of the below query, which is what i think you are after.
SELECT users.name_surname, users.avatar,
GROUP_CONCAT(DISTINCT words_en.word Order by words_en.word asc) AS words
FROM
(
SELECT f1.asker_user_id AS friend_id
FROM friends AS f1
LEFT JOIN friends AS f2
ON f1.asked_user_id = f2.asker_user_id
AND f1.asker_user_id = f2.asked_user_id
WHERE f1.status = 1 AND f2.status IS NULL
AND f1.asked_user_id = 2
) AS MainQ
INNER JOIN users ON MainQ.friend_id = users.id
INNER JOIN connections ON users.id = connections.user_id
INNER JOIN words_en ON words_en.id = connections.word_id
I have 3 MySQL tables namely chat_comments, chat_friends and user_details and I want to display a friend list.
My tables:
chat_comments(comment_id,comment,user_id,user_id2,date_added)
chat_friends(user_id,user_id2,approved)
user_details(user_id, mainimage_id, fullname)
To do this, I need a query that will return the needed fields (u.mainimage_id, u.fullname, b.comment, b.user_id) so I can loop through the list to display a table.
SQL so far (help from #Andriy M):
SELECT
cc.comment,
cc.date_added,
u.fullname,
u.mainimage_id
FROM
user_details u
LEFT JOIN
chat_comments cc
INNER JOIN (
SELECT
user_id,
MAX(comment_id) AS maxcomment
FROM chat_comments WHERE user_id=2020 OR user_id2=2020
GROUP BY user_id
) a ON a.user_id = cc.user_id
AND a.maxcomment = cc.comment_id
ON a.user_id = u.user_id
WHERE u.user_id IN (
SELECT user_id2
FROM chat_friends
WHERE user_id = 2020
AND approved = 1
)
The above query returns the last comment made by the logged-in user's friends in conversation not the last comment between the logged-in user and his/her friend regardless of who made it.
I would like it to return the last comment between the logged-in user and their friend individually regardless of who made it. In the chat_messages table, user_id is the sender and user_id2 is the receiver. Hope it makes sense?
Like #imm said in a comment, you need to use an outer join. In case of a left join, the user_details table should become the left side of the join, the right side being the result of your inner join of chat_comments with your a derived table. You'll also need to remove the user_id IN (…) condition from inside the a subselect and re-apply it to the user_details table. Here:
SELECT
cc.comment,
cc.date_added,
u.fullname,
u.mainimage_id
FROM
user_details u
LEFT JOIN
chat_comments cc
INNER JOIN (
SELECT
user_id,
MAX(comment_id) AS maxcomment
FROM chat_comments
GROUP BY user_id
) a ON a.user_id = cc.user_id
AND a.maxcomment = cc.comment_id
ON a.user_id = u.user_id
WHERE u.user_id IN (
SELECT user_id2
FROM chat_friends
WHERE user_id = 2020
AND approved = 1
)
;
Alternatively, you could use a right join. In this case you would just need to move the user_id IN (…) condition, similarly to the LEFT JOIN solution above, and replace the second INNER JOIN with RIGHT JOIN:
SELECT
cc.comment, cc.date_added, u.fullname, u.mainimage_id
FROM
(
SELECT user_id, MAX(comment_id) AS maxcomment
FROM chat_comments
GROUP BY user_id
) a
INNER JOIN
chat_comments cc ON
a.user_id = cc.user_id AND
a.maxcomment = cc.comment_id
RIGHT JOIN
user_details u ON
a.user_id = u.user_id
WHERE u.user_id IN (select user_id2 from chat_friends where user_id=2020 AND approved=1)
My database have got 4 table :
users
id
username
images
id
user_id
image
user_follow
user_id
user_follow
commentaries
image_id
text
I try to make a query to get all my and my friends pictures
1) row must be shown only if user have picture in "images" table
2) only image from me and my friends (depending on "user_follow" table)
3) count commentaries for each picture
my query is:
SELECT u.username as user, i.image as user_image, p.image, UNIX_TIMESTAMP(p.date) as date, COALESCE ( imgcount.cnt, 0 ) as comments
FROM users u
LEFT JOIN user_follow f ON u.id = f.follow_id
LEFT JOIN images p ON p.user_id = u.id
LEFT JOIN images i ON i.id = (SELECT b.id FROM images AS b where p.user_id = b.user_id ORDER BY b.id DESC LIMIT 1)
LEFT JOIN (SELECT image_id, COUNT(*) as cnt FROM commentaries GROUP BY image_id ) imgcount ON p.id = imgcount.image_id
WHERE f.user_id = 3 OR p.user_id = 3
ORDER BY p.date DESC
Commentaries count of each image sql line works fine in this query
LEFT JOIN (SELECT image_id, COUNT(*) as cnt FROM commentaries GROUP BY image_id ) imgcount ON p.id = imgcount.image_id
in this line I try to get user his last upload image as avatar from "images" table
LEFT JOIN images i ON i.id = (SELECT b.id FROM images AS b where p.user_id = b.user_id ORDER BY b.id DESC LIMIT 1)
This query dot not return result correctly because it show my friends who do not have pictures and something is not good with my own pictures (in database I have 2 row with my user_id : 3 ) but sql return 4
If I'm understanding correctly, it seems like you've made this a lot more complex than it needs to be. The reason you are getting records for your friends without pictures is because you are using a LEFT JOIN. Change that to an INNER JOIN and you will only get the records that match the join condition.
I think you are looking for something like the following. You'll need to make a few tweaks but hopefully this helps.
SELECT u.username as user, i.image as user_image, count(*) as comments
FROM users u
INNER JOIN user_follow f ON u.id = f.follow_id
INNER JOIN images p ON p.user_id = u.id
INNER JOIN commentaries c ON c.image_id = p.id
WHERE u.user_id = 3
GROUP BY u.username, i.image;