Im newbie please help me on my project. I have 2 tables below.
Table user:
Table Likes
I want to count all likes per story_id and check if the given user has like the story else it will return null.
as of now this is my query and output, given user id = 1.
SELECT COUNT(*) , sl.story_id, u.id as user
FROM stories_likes sl
LEFT JOIN users u ON sl.user_id = u.id AND sl.user_id = 1
GROUP BY sl.story_id
My output:
But what i want to get output is:
Given: user_id = 1
Given user_id = 4
Sorry for the construction of my question i dont know how. Thanks in advance
If the query should display the result for a one particular user_id only then try the following query:
select count(*),
story_id,
(case find_in_set(1, Group_concat(user_id separator ',')) >0 then 1
else NULL
end
)as user_id
from Stories_Likes
group by story_id;
In above query, you can put user_id manually after when, or you can set a variable with particular Id and use it in the query.
For i.e., if you want to check for user_id=4, then put 4 after when and then.
Click here for the Updated Demo
Hope it helps!
The users table is left joined to the query, so it may have null values. Instead, you should use the user_id column from the stories_likes table:
SELECT COUNT(*) , sl.story_id, sl.user_id as user
-- Here --------------------------^
FROM stories_likes sl
LEFT JOIN users u ON sl.user_id = u.id AND sl.user_id = 1
GROUP BY sl.story_id
Got the answer. for those who has the same problem and needed this here's the answer.
SELECT COUNT(*) , sl.story_id, t.user_id
FROM stories_likes sl
LEFT JOIN users u ON sl.user_id = u.id
LEFT JOIN (SELECT * FROM stories_likes WHERE user_id = 4) t ON
sl.story_id = t.story_id
GROUP BY sl.story_id
Where the given user is declared on temporary table t
Related
I have query which looks like:
SELECT * FROM
( SELECT DISTINCT CASE
WHEN user1_id = 1
THEN user2_id
ELSE user1_id
END userID,conversationId
FROM conversations
WHERE 1 IN (user2_id,user1_id))dt
INNER JOIN users on dt.userID = users.id
It returns conversationId and information about user from users table. I would like to also add the last message (the one with biggest messageId) from message table on base of conversationId. The last thing would be to sort all the results by messageId
I tried to use another INNER JOIN which looked like :
INNER JOIN message on dt.conversationId = message.conversationId
Its adding messages to the result but I would like to get only the last one (the one with highest messageId as mentioned). I guess I would have to implement MAX somehow but I dont have idea how. The same thing with sorting all result by messageId so results with the biggest messageId would be first.
Thanks for all suggestions.
You can get the highest messageId for the conversation in a corelated subquery and use it for your join condition:
INNER JOIN message m
on m.conversationId = dt.conversationId
and m.messageId = (
SELECT MAX(m1.messageId)
FROM message m1
WHERE m1.conversationId = dt.conversationId
)
So the solution for eveything was following query
SELECT * FROM
( SELECT DISTINCT
CASE
WHEN user1_id = 1
THEN user2_id
ELSE user1_id
END userID,conversationId
FROM conversations
WHERE 1 IN (user2_id,user1_id))dt
INNER JOIN users on dt.userID = users.id
INNER JOIN message m on m.conversationId = dt.conversationId and m.messageId = (SELECT MAX(m1.messageId)
FROM message m1 WHERE m1.conversationId = dt.conversationId)
ORDER by m.messageId DESC
I have 2 tables: user and review, a one-to-many relationship.
When I execute the following query:
SELECT
user_id,
count(*) totalReviews,
USER . NAME
FROM
review,
USER
WHERE
USER .id = review.user_id
GROUP BY
user_id
I get:
1 2 marius
2 2 daniela
3 1 alin
What I want to do now is to display first 2 users because they have given the most reviews(2).
I tried adding having, if I hardcode having totalReviews=2 it works, but if I write having total = max(total) I get 0 results, while if I'm trying with,
SELECT
*
FROM
(
SELECT
user_id,
count(*) total,
USER . NAME
FROM
review,
USER
WHERE
USER .id = review.user_id
GROUP BY
user_id
) A
WHERE
total = (SELECT max(total) FROM A) `
I get an error (table A doesn't exist)
You would do this with ORDER BY and LIMIT:
SELECT u.id, count(*) as totalReviews, u.name
FROM review r JOIN
user u
ON u.id = r.user_id
GROUP BY u.id, u.name
ORDER BY totalReviews DESC
LIMIT 2;
Notes:
Never use commas in the FROM clause. Always use proper, explicit JOIN syntax.
Table aliases make the query easier to write and read.
EDIT:
If occurs to me that you want all users with the maximum number of reviews, not exactly 2. Here is one method:
SELECT u.id, COUNT(*) as totalReviews, u.name
FROM review r JOIN
user u
ON u.id = r.user_id
GROUP BY u.id, u.name
HAVING totalReviews = (SELECT COUNT(*)
FROM review r2
GROUP BY r2.user_id
ORDER BY COUNT(*) DESC
LIMIT 1
);
Note that the subquery in the HAVING clause is simpler than the outer query. There is no need to bring in the user name.
I want to perform a textsearch on a table containing posts belonging to topics within groups. Depending on the privacysettings for these groups I need to run a subquery to check if the requesting user is a member of the groups containg search matches.
Databasescheme:
Table: posts
Columns: id, group_id, title, text
Table: groups
Columns: group_id, privacy
Table: group_memberships
Columns: group_id, is_member
The privacy column in the group table contains an integervalue.
1 = public, anyone can access the data
2 = system, anyone can access the data
3 = private, only members can access the data
What the query should do:
1. Find some matches in the post table
2. Check the group privacy in the groups table -> a value HIGHER THAN 2 requires a membership check
3. Do a membership check on the group_memberships table if required
I really don't know how do handle this.
It looks like mysql supports two ways? IF statements and case expressions?
What would be a correct way for this?
PS: The subquery for membership checking should be optional and only firing if needed.
Something "like" this..
Pseudocode:
SELECT p.id, p.title, p.text
FROM posts p
INNER JOIN groups g
ON g.group_id = p.group_id
AND p.title is not null
WHERE EXISTS(
CASE
WHEN g.privacy < 2 THEN ''everything is ok. Nothing more needed''
ELSE (''Membership check needed'')
END
)
EDIT:
Can someone confirm that this is a/the right way?
SELECT p.id, p.channel_id, p.title, g.name
FROM posts p
INNER JOIN user_groups g
ON g.id = p.channel_id
AND p.title is not null
WHERE g.privacy < 2 OR (SELECT count(*) FROM user_groups_memberships WHERE uid = 1 AND channel_id = p.channel_id AND rank IS NOT NULL AND is_banned IS NULL) = 1
GROUP BY p.parent_id
Okay this might not be the best answer, but this solves the above problem without using IF or CASE expressions.
select
p.id,
p.group_id,
p.title,
p.text
from
posts p,
groups g
where
p.group_id = g.group_id
and
(
g.privacy<3
or
( g.privacy => 3 and
(select is_member from group_memberships gm where gm.group_id = g.group_id) = 1)
);
Assuming here that is_member = 1 means that id is a member and 0 means that id isn't.
Good day, I can't seem to figure out how to do this. I'll first explain my database model:
User (user_id, name)
Job (job_id, name)
UserTopJob (user_id, job_id)
UserOtherJob(user_id, job_id)
A user can setup his top jobs which he likes best. Those values will be saved into UserTopJob by the user_id and the job_id. The user can set some other jobs he likes into UserOtherJob as well.
Now, what I want to do is query out users that match my job search input.
For example, the search input is job_id 1 and 2.
Now I want to query out the users that match BOTH job_id 1 and job_id 2, but it doesn't matter whether they are in the users top or other jobs, or divided between those two tables.
So a user must be returned if:
Both job_id 1 & 2 are in top jobs
Both job_id 1 & 2 are in the other jobs
They have both job_id 1 and 2 but in different tables
The number of input ids can grow and does not have a limit. It must always match ALL input values.
Edit: So, for example if I'm putting job_ids 1 and 2 and 3 into the query, the ids 1 AND 2 AND 3 need to be in the top or other table for that user.
Can anybody please help me create a MySQL-query that can do this and doesn't put too much pressure on db-performance?
Thanks in advance for helping me out here!
You can use UNION for this type of work.
SELECT user_id AS user FROM UserTopJob where job_id in {job_ids}
UNION
SELECT user_id AS user FROM UserOtherJob where job_id in {job_ids};
Try this query:
SELECT u.*
FROM User u
WHERE NOT EXISTS (
SELECT 1
FROM User u0
JOIN Job j ON j.job_id IN (1,2) -- or other list of job ids
LEFT JOIN UserTopJob utj ON utj.user_id = u0.user_id AND utj.job_id = j.job_id
LEFT JOIN UserOtherJob uoj ON uoj.user_id = u0.user_id AND uoj.job_id = j.job_id
WHERE u0.user_id = u.user_id
AND utj.job_id IS NULL
AND uoj.job_id IS NULL
)
Test in on SQL Fiddle
You can do a JOIN between the tables to get the required result like
select u.name as user_name,
j.name as job_name
from `user` u
INNER join usertopjob utj on u.user_id = utj.user_id
inner join userotherjob uoj on u.user_id = uoj.user_id
inner join job j on j.job_id = utj.job_id or j.job_id = uoj.job_id
where j.job_id in (1,2);
Alright, this was a brain buster this evening. Toying around with this for some time I came up with this and it seems to work.
SELECT user_id, SUM(matched) AS totalMatched FROM
(
SELECT uoj.user_id, COUNT(uoj.job_id) AS matched FROM userOtherJob AS uoj
INNER JOIN user AS u ON u.user_id = uoj.user_id
WHERE uoj.job_id IN (1,2)
GROUP BY u.user_id
UNION ALL
SELECT utj.user_id, COUNT(utj.job_id) AS matched FROM userTopJob AS utj
INNER JOIN user AS u ON u.user_id = utj.user_id
WHERE utj.job_id IN (1,2)
GROUP BY u.user_id
) AS t
GROUP BY user_id
HAVING totalMatched = 2
This query counts the matches in the 'other' table, after that the matches in the 'top' table, and sums the totals of both tables. So, the total number of matches (combined from top and other) must be the same value as the number of jobs we're looking for.
I am trying to get all favorite users of a particular user using this simple sub-query
select * from users u
where u.user_id in
(
select GROUP_CONCAT(f.favorite_id SEPARATOR ',') as favourites
from favourite_user f
where f.user_id in(14) group by user_id
)
When I run the subquery select GROUP_CONCAT(f.favorite_id SEPARATOR ',') as favourites
from favourite_user f
where f.user_id in(14) group by user_id it gives me result 6,8,11,10,13,15,7,12
and when i run this query select * from users u
where u.user_id in (6,8,11,10,13,15,7,12) it is returning 7 rows of result
But when i run the above mentioned main query it is just giving me the 1 row (the first one) instead of 7.
Can anyone explain me what am i doing wrong. I know this can also be done with joins but I'd like to know why this approach isn't working
Thank you in advance
You don't need GROUP_CONCAT(). Try
select *
from users
where user_id in
(
select favorite_id
from favourite_user
where user_id = 14
)
Here is SQLFiddle demo