I have two tables:
USER:
userID | uName |
-----------------
1 | John
2 | Bohn
3 | Kohn
4 | Lohn
5 | Zohn
6 | Rohn
IMAGES:
imageID | url | userID
----------------------
1 | x | 2
2 | x | 2
3 | x | 1
4 | x | 3
5 | x | 3
6 | x | 3
As you can see there is USER database which connects to IMAGES database by userID.
There is only one unique user row but there can be more than one image per user.
What i want is to fetch ONE RANDOM user from database and all of his images. Condition is that user should not be selected if he has no images.
Can you help me build ONE mysql query to achieve that?
P.S. It doesnt matter if user data duplicates (because of multiple image rows), there is only one user in resultset anyways.
First, INNER JOIN both tables, to exclude users that don't have any images; then, ORDER BY RAND(), to randomize the resultset; finally, select the first row to obtain a random userId:
SELECT u.*
FROM user u INNER JOIN images i ON (u.userId = i.userId)
ORDER BY RAND()
LIMIT 1
DEMO.
EDIT: To select all images from a random user, use the following:
SELECT i.*
FROM images i
INNER JOIN
(SELECT u.userId
FROM user u INNER JOIN images i ON (u.userId = i.userId)
ORDER BY RAND()
LIMIT 1) rand_user
ON (i.userId = rand_user.userId);
DEMO.
Related
Im not even sure what the title of this question should be but lets start out with my data.
I have a table of users who have taken a few lessons while belonging to a particular training center.
lesson table
id | lesson_id | user_id | has_completed
----------------------------------------
1 | asdf3314 | 2 | 1
2 | d13saf12 | 2 | 1
3 | a33adff5 | 2 | 0
4 | a33adff5 | 1 | 1
5 | d13saf12 | 1 | 0
user table
id | center_id | ...
----------------------------------------
1 | 20 | ...
2 | 30 | ...
training center table
id | center_name | ...
----------------------------------------
20 | learn.co | ...
30 | teach.co | ...
I've written a small chunk but am now stuck as I don't know how to proceed. This statement gets the counted total of completed lessons per user. it then figures the average completed value from a center id. if two users belong to a center and have completed 3 lessons and 2 lessons it finds the average of 3 and 2 then returns that.
SELECT
FLOOR(AVG(a.total)) AS avg_completion,
FROM
(SELECT
user_id,
user.center_id,
count(user_id) AS total
FROM lesson
LEFT JOIN user ON user.id = user_id
WHERE is_completed = 1 AND center_id = 2
GROUP BY user_id) AS a;
The question I have is how do I loop through the training centers table and also append average data from similar select statement as above to each center that is queried. I cant seem to pass the center id down to the subquery so there must be a fundamentally different way to achieve the same query but also loop through training centers.
An example of desired result:
center.id | avg_completion | ...training center table
-----------------------------------------------------
20 | 2 | ...
Your main query needs to select a.center_id and then use GROUP BY center_id. You can then join it with the training_center table.
SELECT c.*, x.avg_completion
FROM training_center AS c
JOIN (
SELECT
a.center_id,
FLOOR(AVG(a.total)) AS avg_completion
FROM (
SELECT
user_id
user.center_id,
count(*) AS total
FROM lesson
JOIN user ON user.id = user_id
WHERE is_completed = 1 AND center_id = 2
GROUP BY user_id) AS a
GROUP BY a.center_id) AS x
ON x.center_id = c.id
If I understand correctly:
select u.center_id, count(*) as num_users,
sum(l.has_completed) as num_completed,
avg(l.has_completed) as completed_ratio
from lesson l join
user u
on l.user_id = u.id
group by u.center_id
I have 2 mysql tables namely 'properties' and 'images'.
Properties
+------------+---------------+
| propertyId | propertyTitle |
+------------+---------------+
| 1 | 1 acre land |
| 2 | 2 acre land |
| 3 | 3 acre land |
+------------+---------------+
Images
+---------+---------------+---------------+
| imageId | image | propertyId |
+---------+---------------+---------------+
| 1 | land.jpeg | 1 |
| 2 | landview.jpg | 1 |
| 3 | viewland.jpeg | 2 |
+---------+---------------+---------------+
They have a one-many relationship and the images table has a foreign key of the properties table. I would like to perform a query that selects a property and then selects a single image of the property.
The query i'm trying to work with is
SELECT * FROM properties p
JOIN (SELECT * FROM images im LIMIT 1)
ON im.propertyId = p.propertyId;
Its not working though. Neither does it return an error.
If you want returns all rows, your query will become:
SELECT * FROM properties p
JOIN images im
ON im.propertyId = p.propertyId;
Using LIMIT 1 you return only one row from your images table so you have a limitation about your rows
EDIT
After comments:
In this way you'll get the first image linked to your property.
SELECT p.*,
(SELECT im.mage
FROM images im
WHERE im.propertyId = p.propertyId
AND NOT EXISTS (
SELECT 'NEXT'
FROM images im2
WHERE im.propertyId = im2.propertyId
AND im2.imageId > im.imageId)
)
FROM properties p;
We can handle this problem using two joins. First, join the properties table to the images table as you suspected in your question. Then, do an additional to join to a subquery which finds the first image for each property.
SELECT
p.propertyId,
p.propertyTitle,
i1.image
FROM properties p
INNER JOIN images i1
ON p.propertyId = i1.propertyId
INNER JOIN
(
SELECT propertyId, MIN(imageId) AS min_imageId
FROM images
GROUP BY propertyId
) i2
ON i1.propertyId = i2.propertyId AND
i1.imageId = t2.min_imageId;
Try below query,
SELECT * FROM properties p
JOIN images im
ON im.propertyId = p.propertyId
where p.propertyTitle = '1 acre land'
LIMIT 1
I have 3 tables i want to join all tables each other. But my 3rd table not working.
See my table -
users
id | username |is_active
----------|----------------|------------
1 | chinu | 1
2 | sradhanjali | 1
3 | User3 | 0
settings
id | user_id | public_msg_notification
----------|-----------|---------------------------
1 | 1 | 1
2 | 2 | 1
3 | 3 | 1
friends
id | user_id | friend_id | is_block
----------|-----------|---------------------------
1 | 3 | 1 | 0
2 | 1 | 2 | 1
3 | 3 | 2 | 0
Query
SELECT a.username FROM users a
JOIN settings b
JOIN friends c ON(a.id=c.user_id OR a.id=c.friend_id)
WHERE a.username IN('john','piter','rahul','sradhanjali')
AND a.id != '1' AND a.is_active=1
AND a.id=b.user_id AND b.public_msg_notification=1
AND c.is_block=0 GROUP BY a.username
I have run this query in my local only sradhanjali username fetched. But this user is_block=1 in the friends table.
I think My third table friends not working. I want to show that result those usernmes where is_block=0. In above data my output should be zero(0) But I am getting 1 record while execute above query.
We had a chat discussion and I think this question is not meant to be on SO for the most part. I did promise if I could figure it out I would try to provide some insight. At this point I think this is a correct approach, but it is very specific to this instance.
SELECT u.username FROM users u
JOIN (SELECT
IF(u.id=f.user_id, f.friend_id, f.user_id) as ids
FROM users u
JOIN friends f ON (f.user_id=u.id OR f.friend_id=u.id)
WHERE
u.id=$SOME_ID AND f.is_block=0) friends ON (u.id=friends.ids)
JOIN settings s ON (s.user_id=friends.ids)
WHERE s.public_msg_notification=1 AND u.is_active=1
GROUP BY friends.ids
By trying to be too specific you aren't able to open up the query any more and have to do a nested query inside. This should get all users you are friends with THEN see which users are accepting public notifications and are active. I'm fearing this will fail. But this at the least will put you in the right direction.
I have the following (simplified) three tables:
user_reservations:
id | user_id |
1 | 3 |
1 | 3 |
user_kar:
id | user_id | szak_id |
1 | 3 | 1 |
2 | 3 | 2 |
szak:
id | name |
1 | A |
2 | B |
Now I would like to count the reservations of the user by the 'szak' name, but I want to have every user counted only for one szak. In this case, user_id has 2 'szak', and if I write a query something like:
SELECT sz.name, COUNT(*) FROM user_reservations r
LEFT JOIN user_kar k ON k.user_id = r.user_id
LEFT JOIN szak s ON r.szak_id = r.id
It will return two rows:
A | 2 |
B | 2 |
However I want to every reservation counted to only one szak (lets say the highest id only). I tried MAX(k.id) with HAVING, but seems uneffective.
I would like to know if there is a supported method for that in MySQL, or should I first pick all the user ID-s on the backend site first, check their maximum kar.user_id, and then count only with those, removing them from the id list, when the given szak is counted, and then build the data back together on the backend side?
Thanks for the help - I was googling around for like 2 hours, but so far, I found no solution, so maybe you could help me.
Something like this?
SELECT sz.name,
Count(*)
FROM (SELECT r.user_id,
Ifnull(Max(k.szak_id), -1) AS max_szak_id
FROM user_reservations r
LEFT OUTER JOIN user_kar k
ON k.user_id = r.user_id
GROUP BY r.user_id) t
LEFT OUTER JOIN szak sz
ON sz.id = t.max_szak_id
GROUP BY sz.name;
Here is what I'm trying to do. I have a table with user assessments which may contain duplicate rows. I'm looking to only get DISTINCT values for each user.
In the example of the table below. If only user_id 1 and 50 belongs to the specific location, then only the unique video_id's for each user should be returned as the COUNT. User 1 passed video 1, 2, and 1. So that should only be 2 records, and user 50 passed video 2. So the total for this location would be 3. I think I need to have two DISTINCT's in the query, but am not sure how to do this.
+-----+----------+----------+
| id | video_id | user_id |
+-----+----------+----------+
| 1 | 1 | 1 |
| 2 | 2 | 50 |
| 3 | 1 | 115 |
| 4 | 2 | 25 |
| 5 | 2 | 1 |
| 6 | 6 | 98 |
| 7 | 1 | 1 |
+-----+----------+----------+
This is what my current query looks like.
$stmt2 = $dbConn->prepare("SELECT COUNT(DISTINCT user_assessment.id)
FROM user_assessment
LEFT JOIN user ON user_assessment.user_id = user.id
WHERE user.location = '$location'");
$stmt2->execute();
$stmt2->bind_result($video_count);
$stmt2->fetch();
$stmt2->close();
So my query returns all of the count for that specific location, but it doesn't omit the non-unique results from each specific user.
Hope this makes sense, thanks for the help.
SELECT COUNT(DISTINCT ua.video_id, ua.user_id)
FROM user_assessment ua
INNER JOIN user ON ua.user_id = user.id
WHERE user.location = '$location'
You can write a lot of things inside a COUNT so don't hesitate to put what you exactly want in it. This will give the number of different couple (video_id, user_id), which is what you wanted if I understood correctly.
The query below joins a sub-query that fetches the distinct videos per user. Then, the main query does a sum on those numbers to get the total of videos for the location.
SELECT
SUM(video_count)
FROM
user u
INNER JOIN
( SELECT
ua.user_id,
COUNT(DISTINCT video_id) as video_count
FROM
user_assessment ua
GROUP BY
ua.user_id) uav on uav.user_id = u.user_id
WHERE
u.location = '$location'
Note, that since you already use bindings, you can also pass $location in a bind parameter. I leave this to you, since it's not part of the question. ;-)