Sorry if this is a silly question, I searched a bit and couldn't find a solution for an example like mine.
I've got a small photo sharing app with a query which outputs the ID numbers of users, ordered by the number of followers they have. I want to alter the query slightly so that if users have the same number of followers, they will be ordered by the number of photos they've uploaded instead.
How would I go about editing my query? All attempts I've made have been unsuccessful.
Current query looks like this:
SELECT Users.ID, COUNT(User_Followers.FollowingUserID)
AS follower_count FROM Users
LEFT JOIN User_Followers ON Users.ID = User_Followers.FollowingUserID
GROUP BY Users.ID
ORDER BY follower_count DESC
Where the User_Followers table looks like this:
ID UserID FollowingUserID DateFollowed
And the photos table looks like this:
ID PostedByUserID DatePosted
Thanks in advance for any help!
SELECT Users.ID,
COUNT(User_Followers.FollowingUserID) AS follower_count
FROM Users
LEFT JOIN User_Followers
ON Users.ID = User_Followers.FollowingUserID
LEFT JOIN
(
SELECT PostedByUserID, COUNT(*) postCount
FROM photos
GROUP BY PostedByUserID
) a ON Users.ID = a.PostedByUserID
GROUP BY Users.ID
ORDER BY follower_count DESC, a.postCount DESC
Related
There are three tables, I would like to get the count of a user's total tweets and the count of likes his total tweets received.
I tried to combine two queries to get what I want but failed. Have looked through several previous questions but still can't figure it out.
Users table
id
name
1
User1
Tweets table
id
UserId (foreign key)
content
1
User1
hello
Likes table
id
UserId (foreign key)
TweetId (foreign key)
1
User1
hello
First query:
SELECT Users.name, Users.id, COUNT(Tweets.UserId) AS UserTweetCount FROM Users
LEFT JOIN Tweets
ON Users.id = Tweets.UserId
GROUP BY Users.id
ORDER BY UserTweetCount DESC;
Second query:
SELECT Users.name, Users.id, COUNT(Likes.UserId) AS UserTweetBeLikedCount FROM Users
LEFT JOIN Likes
ON Users.id = Likes.UserId
GROUP BY Users.id;
I tried like below but would get wrong UserTweetBeLikedCount counts. The counts would be UserTweetCount's, not UserTweetBeLikedCount's. When I ran two queries separately, it worked well. But when I combined them together, it didn't work right.
Don't know how to display the right counts. Can someone give me hints to solve this, please?
SELECT Users.name, Users.id,
COUNT(Tweets.UserId) AS UserTweetCount, COUNT(Likes.UserId) AS UserTweetBeLikedCount
FROM Users
LEFT JOIN Tweets
ON Users.id = Tweets.UserId
LEFT JOIN Likes
ON Users.id = Likes.UserId
GROUP BY Users.id
ORDER BY UserTweetCount DESC;
I recommend using correlated subqueries for this:
SELECT u.*,
(SELECT COUNT(*)
FROM Tweets t
WHERE u.id = t.UserId
) AS UserTweetCount,
(SELECT COUNT(*)
FROM Likes l
WHERE u.id = l.UserId
) AS UserLikeCount
FROM Users u
ORDER BY UserTweetCount DESC;
As a note: For performance, you want indexes on Tweets(UserId) and Likes(UserId).
I have the following query:
SELECT users.id, username FROM users
where exists (select 1 from topic_visits tv where users.id = tv.user_id and topic_id = 2)
order by tv.created_at;
I want to retrieve all users who have visited topic 2 in ascending order (oldest visit first).
I got this error: #1054 - Unknown column 'tv.created_at' in 'order clause'.
You can change your query as shown below:
SELECT distinct users.id, username,tv.created_at
FROM users
join topic_visits tv ON users.id = tv.user_id and topic_id = 2
order by tv.created_at
tv is in the sub-query, it doesn't exist at the top level.
using a join, we group by users.id so there is a unique list of users.
As the tv.created_at could be multiple we need to wrap it in an aggregate function, in this case MAX. Maybe MIN suites your needs better however.
SELECT users.id, username
FROM users
join topic_visits tv ON users.id = tv.user_id and topic_id = 2
group by users.id
order by MAX(tv.created_at);
I have a table posts with columns board_id, author_id, message. I have another table users with columns id, name, avatar_url.
I need to write a query to get all of the users that have posted on a given board, with no duplicates. The query should return the full user row (id, name, avatar_url).
I've tried
SELECT DISTINCT users.*, posts.author_id
FROM users
INNER JOIN posts
ON users.id = posts.author_id
WHERE posts.board_id = [desired board ID]
but that's giving me duplicates of each user.
There is also the possibility that my query is correct and I've goofed on something elsewhere...
Here's a simple query that will get you all the rows in users with post activity w/o duplication
SELECT * FROM USERS
WHERE id IN (SELECT author_id FROM posts WHERE board_id = [desired board]
You could also use your basic syntax with a distinct on everything you need distinct, e.g.:
SELECT DISTINCT users.*
FROM users
JOIN posts ON users.id = posts.author_id
WHERE posts.board_id = [desired board ID]
Just group by the user id, like so:
SELECT users.id, MIN(users.name), MIN(users.avatar_url)
FROM users
INNER JOIN posts
ON users.id = posts.author_id
WHERE posts.board_id = [desired board ID]
GROUP BY users.id
SELECT users.id, users.name, users.avatar_url, posts.author_id
FROM users
INNER JOIN posts
ON users.id = posts.author_id
WHERE posts.board_id = [desired board ID] GROUP BY users.id
This will get all found rows and then group them by the userid so each user id will appear just once, hence each user row [who posts on the board] will appear just once.
Yet better is use with annotation not for highlighted after IN, which defense against duplicate values. That's it.
I'm stuck doing a query. I'd like to extract the 10 first records of one table considering the values of the other three tables. I'll try to explain what I want with an example:
TABLES
USERS: username and date
POINTS: id_user, points
COMMENTS: id_user
WON: id_user
THE CRITERIA MUST BE: The 10 users who have more points and, in case of equal values, with more comments published, less recent date date and didn't won. In that order.
SELECT id, username, date FROM users as us LIMIT 10 ORDER BY date DESC JOIN id_user, points FROM points as po WHERE us.id = po.id_user ORDER BY po.points DESC JOIN COUNT (id_user) FROM comments JOIN COUNT (id_user) FROM won;
I know that's wrong... :(
Assuming Users has an id field and a created datetime field, I think you're looking for something like this
SELECT *
FROM Users
LEFT JOIN Points ON Points.id_user = Users.id
LEFT JOIN Comments ON Comments.id_user = Users.id
LEFT JOIN Won ON Won.id_user = Users.id
GROUP BY Users.id
ORDER BY SUM(Points.points) DESC, COUNT(Comments.id) DESC, MAX(Users.created) DESC, COUNT(Won.id) DESC
I need to build an activity feed to go on each users profile page showing what they have been doing on the site.
There is three tables: comments, ratings, users
I want the feed to include the comments and ratings that the user has posted.
in the comments and ratings table it stores the user id of the user who posted it, not the username, so in for each item in the news feed it needs to select from the users table where the user id is the same to retrieve the username.
All the entries in the feed should be ordered by date.
Here is what ive got even though i know it is not correct because it is trying to match both with the same row in the users table.
SELECT comments.date, comments.url AS comment_url, comments.user_id, ratings.date, ratings.url AS rating_url, ratings.user_id, users.id, users.username
FROM comments, ratings, users
WHERE comments.user_id=%s
AND comments.user_id=users.id
AND ratings.user_id=%s
AND ratings.user_id=users.id
ORDER BY ratings.date, comments.date DESC
JOIN. It seems you know that, but here's how:
SELECT * FROM comments LEFT JOIN users ON comments.user_id = users.id
Thus, as far as I can tell, you're trying to order two separate things at the same time. The closest I think I can come up with would be something like:
(SELECT comments.date AS date, users.username AS name, comments.url AS url CONCAT('Something happened: ',comments.url) AS text
FROM comments LEFT JOIN users ON comments.user_id = users.id
WHERE users.id = %s)
UNION
(SELECT ratings.date AS date, users.username AS name, ratings.url AS url CONCAT('Something happened: ',ratings.url) AS text
FROM comments LEFT JOIN users ON comments.user_id = users.id
WHERE users.id = %s)
ORDER BY date DESC LIMIT 0,10
Note that the columns of both parts of the union match up. I'm pretty sure that that is required for something like this to work. That's why I have that CONCAT statement, which lets you build a string that works differently between ratings and comments.