Afternoon folks,
I have had a good dig around and can't find the answer, so a good time to ask!
I'd like to select random rows from one table and then join into this random rows from another table where the ID that I have is the same. It would also be great to only select where I have an entry in the second table. I have tried all manner of sub-queries but am getting a bit lost. An inner join as read will do it but again with the randomness of it all!! Grrr...
SELECT
tracks.track_id,
cuttings.square_cutting,
cuttings.cutting_2,
cuttings.cutting_3,
cuttings.blog_text
FROM tbl_tracks tracks,
(SELECT
square_cutting,
cutting_2,
cutting_3,
blog_text
FROM
tbl_cuttings
WHERE track_id = tracks.track_id <-- wont find it, obviously!!
ORDER BY RAND()
LIMIT 1) cuttings
WHERE tracks.active = '1' ORDER BY RAND()
Thanks in advance for any help.
So:
I'd like random tracks showing
track id -> with random cuttings, of which there can be many but I just want 1.
It would then be ideal to only show a result if there is a cutting associated with that track.
Hope that helps.
I'm now trying to go a step further with this and order this by a RAND() seed as I'm now having to add in pagination. Only problem is that its not giving me back the same random list due to a given seed. Any Ideas?
SELECT
tracks.track_id,
cuttings.square_cutting,
cuttings.cutting_2,
cuttings.cutting_3,
cuttings.blog_text
FROM tbl_tracks tracks
INNER JOIN
(SELECT track_id,
square_cutting,
cutting_2,
cutting_3,
blog_text
FROM
tbl_cuttings
ORDER BY RAND()) cuttings ON tracks.track_id = cuttings.track_id
WHERE tracks.active = '1'
ORDER BY RAND(1)
LIMIT 0,4;
you could use an inner join
SELECT
tracks.track_id,
cuttings.square_cutting,
cuttings.cutting_2,
cuttings.cutting_3,
cuttings.blog_text
FROM tbl_tracks tracks
INNER JOIN
(SELECT track_id,
square_cutting,
cutting_2,
cutting_3,
blog_text
FROM
tbl_cuttings
ORDER BY RAND()
LIMIT 1) cuttings on cuttings.track_id = tracks.track_id
WHERE tracks.active = '1'
ORDER BY RAND()
Related
I have a problem with mysql - i'm kind new to it, byt looking to improve my skills :)
Have a code like this:
if($where > 0) $query = mysql_query("SELECT img.*, user.user as owner_name, cat.name as cat_name FROM tentego_img AS img LEFT JOIN tablicacms_users AS user ON user.id = img.owner LEFT JOIN tentego_img_cat AS cat ON cat.id = img.cat WHERE img.`is_waiting` LIKE ".$where.$cat." INNER JOIN tentego_img_vote ON tentego_img.id = tentego_img_vote.object_id GROUP BY tentego_img_vote.object_id ORDER BY SUM ( (CASE WHEN tentego_img_vote.vote = '0' THEN '-1' ELSE '1' END) ) DESC LIMIT ".$page.",".$objPerPage);
I need to make sorting by number of votes, sorted descending.
Still it makes results sorted by it own way.
In table I have rows:
ID - vote id for table purpose
object_id- id of object joined with another table to show results.
User ID - user id
Vote - where values are 0 for dislike and 1 for like (so -1 for 0, and +1 for 1)
So, as I understand i need to sum up all records for each of unique object_id, then sort by sum of vote values of each.
This code worked before my script provider decide to upgrade it, so right now i dont know how to fix it :(
I am facing serious issue in my workout related to PHP and MySql on Linux server while when am running same code with same database in localhost, it's working fine.
As well as I have almost 30,000 records in database table and mysql is:
SELECT * FROM tbl_movies where id not in (select movie_id from tbl_usermovieque where user_id='3' union
select movie_id from tbl_user_movie_response where user_id='3' union
select movie_id from tbl_user_movie_fav where user_id='3') and id < 220 order by rand() limit 0,20
its taking 0.0010 sec in my localhost and INFINITE on our linux server. i unable to find the reason.
Thanks
Kamal
Can you confirm this return the same result ? It should be faster this way. Union are usefull sometime but not really optimized.
SELECT * FROM tbl_movies where id not in (
select distinct movie_id
from tbl_movies m
inner join tbl_usermovieque um ON um.movie_id = m.movie_id = m.movie_id
inner join tbl_user_movie_response umr ON umr.movie_id = m.movie_id = m.movie_id
inner join tbl_user_movie_fav umf ON umf.movie_id = m.movie_id = m.movie_id
where um.user_id = 3 or umr.user_id = 3 or umf.user_id = 3
) and id < 220 order by rand() limit 0,20;
PS : I assume you have Index un oser_id and id_movie
EDIT : your problem may come from rand()
MySQL order by optimization Look for RAND() in the page : in comment there are some performance test => rand() alone seams to be a bad solution
Performance
Now let's see what happends to our performance. We have 3 different
queries for solving our problems.
Q1. ORDER BY RAND()
Q2. RAND() * MAX(ID)
Q3. RAND() * MAX(ID) + ORDER BY ID
Q1 is expected to cost N * log2(N), Q2 and Q3 are nearly constant.
The get real values we filled the table with N rows ( one thousand to
one million) and executed each query 1000 times.
Rows ||100 ||1.000 ||10.000 ||100.000 ||1.000.000
Q1||0:00.718s||0:02.092s||0:18.684s||2:59.081s||58:20.000s
Q2||0:00.519s||0:00.607s||0:00.614s||0:00.628s||0:00.637s
Q3||0:00.570s||0:00.607s||0:00.614s|0:00.628s ||0:00.637s
As you can see the plain ORDER BY RAND() is already behind the
optimized query at only 100 rows in the table.
I've got a problem with two mysql tables. I've done some code and I think I am close to the solution, but I'm not sure if this is right.
So here are the two tables:
Table 1: Blogs
Columns: ID, agp_name, agp_url, agp_username, agp_password
Table 2: Keywords
Columns: ID, agp_user_id, agp_order_id, agp_blog_id, agp_keywords, agp_keywords_date
What I want is to get one random row from Table1 based on the following condition: if the agp_keyword match one of the keywords in the last 5 days then do not include into the result.
So far I did this:
SELECT
t1.agp_user_id, t1.agp_order_id, t1.agp_blog_id, t1.agp_keywords, t1.agp_keywords_date, t2.agp_name, t2.agp_url, t2.agp_username, t2.agp_password
FROM table1 AS t1
INNER JOIN (
SELECT ID, agp_name, agp_url, agp_username, agp_password, agp_blogposts
FROM table2
) AS t2 ON t1.agp_blog_id = t2.ID
WHERE
t1.agp_keywords NOT LIKE "%keyword1%" AND
t1.agp_keywords NOT LIKE "%keyword2%" AND
t1.agp_keywords_date BETWEEN (1369440000 AND 1369932432)
ORDER BY RAND() LIMIT 1
However this does not work correctly. Any help will be appreciated.
Try this, your original specifications were a bit confusing :(
SELECT keywords.agp_user_id,
keywords.agp_order_id,
keywords.agp_blog_id,
keywords.agp_keywords,
keywords.agp_keywords_date,
blogs.agp_name,
blogs.agp_url,
blogs.agp_username,
blogs.agp_password
FROM blogs
LEFT JOIN keywords
ON keywords.agp_blog_id = blogs.ID
AND keywords.agp_keywords NOT LIKE "%keyword1%"
AND keywords.agp_keywords NOT LIKE "%keyword2%"
AND FROM_UNIXTIME(keywords.agp_keywords_date) > (DATE_SUB(CURDATE(), INTERVAL 5 DAYS))
ORDER BY RAND() LIMIT 1
Select 3 rows from table1
Get a specific column data out of each row.
Then use that each column data obtained , to make a query again to get data from table2.
Store the data obtained in step 4 into a variable for each row.
Then put them in json array (table 1 , 3 rows + table 2's data(each of them).
I am building a rank table, it displays top 3 users with their rank name.
For example:
User1 has 2000 points , user 2 has 4000points , user 3 has 10k points , so the top 3 user is :
user 3 > user 2 > user 1
So , i want the php to go to 'users' table and get the top 3 members using this:
$query = mysql_query("SELECT * FROM users ORDER BY pts DESC LIMIT 3");
$rows = array();
while($r = mysql_fetch_assoc($query)) {
$rows[] = $r;
}
Table structure for 'user':
1.username(varchar)
2.pts(int)
After the rows are put into an array , how can i get 'points' for each of the row in that array.
Then go to 'rank' table to get their ranknames.
Table structure for 'rank':
1.rank(varchar)
2.pts(int)
Inside rank table there is 'pts' to let php choose compare which rank the user is at based on the points from each row of the array.
Normally i would use this if its only for 1 user , but for multiple users , im not sure:
$result = mysql_query("SELECT * FROM rank WHERE pts <= '$upts' ORDER BY pts DESC LIMIT 1")
or die(mysql_error());
Then after getting the rank for the top 3 users , php will now add the ranks to each of the user(row) in that array(of course , add it to the rank owner, not just simply place it in).
Then JSON encode it out.
How can i do this?
I am not sure if this is what you want. That is combine the two query into one query. Please take a look at http://sqlfiddle.com/#!2/ad419/8
SELECT user.username,user.pts,rank.rank
FROM user LEFT JOIN rank
ON user.pts <=rank.pts group by user.id
UPDATED:
For extracting top 3, could do as below;
SELECT user.username,user.pts,rank.rank
FROM user LEFT JOIN rank
ON user.pts <=rank.pts
GROUP BY user.id
ORDER BY pts DESC LIMIT 3
If i understand correctly, you need to get values from Rank and Users tables. In order to do that in just one query You need to add FK (Foreign Key) to the Rank table that points to a specific user in the Users table.
So you need to add userId to the Rank table and then you can run:
SELECT r.rank, u.points from users u,rank r where u.userId = r.userId
This is roughly what you need.
Not quite the answer to your exact question, but this might be of use to you: How to get rank using mysql query. And may even mean that you don't require a rank table. If this doesn't help, I'll check back later.
Use this query
$query = "SELECT
u.pts,
r.rank
FROM users as u
left join ranks as r
on r.pts = u .pts
ORDER BY pts DESC
LIMIT 3";
This will bring what you required without putting into an array
$rec = mysql_query($query);
$results = arrau();
while($row = mysql_fetch_row($rec)){
$results[] = $row;
}
echo json_encode($results);
It looks like what you're trying to do is retrieve the rank with the highest point requirement that the user actual meets, which isn't quite what everyone else is giving here. Fortunately it is easily possible to do this in a single query with a nice little trick:
SELECT
user.username,
SUBSTRING_INDEX(GROUP_CONCAT(rank.rank ORDER BY pts DESC),",",1) AS `rank`
FROM user
LEFT JOIN rank ON user.pts >= rank.pts
GROUP BY user.id
ORDER BY pts DESC
LIMIT 3
Basically what the second bit is doing is generating a list of all the ranks the user has achieved, ordering them by descending order of points and then selecting the first one.
If any of your rank names have commas in then there's another little tweak we need to add on, but I wouldn't have thought they would so I've left it out to keep things simple.
This is a more detailed question as my previous attempt wasn't clear enough. I'm new to MySQL and have no idea about the best way to do certain things. I'm building a voting application for images and am having trouble with some of the finer points of MySQL
My db
_votes
id
voter_id
image_id
_images
id
file_name
entrant_id
approved
_users
id
...
Basically I need to do the following:
tally up all votes that are approved
return the top 5 with the most votes
check if the user has voted on each of these 5 (return Boolean) from another table
I've tried variations of
SELECT i.id, i.file_name, i.total_votes
FROM _images i WHERE i.approved = 1
CASE WHEN (SELECT count(*) from _votes v WHERE v.image_id = i.id AND v.voter_id = ?) > 0 THEN '1' ELSE '0' END 'hasvoted'
ORDER BY i.total_votes DESC LIMIT ".($page*5).", 5
is that something I should try and do all in one query?
This query was working fine before I tried to add in the 'hasvoted' boolean:
SELECT id, file_name, total_votes FROM _images WHERE approved = 1 ORDER BY total_votes DESC LIMIT ".($page*5).", 5
At the moment I'm also storing the vote count in the _images table and I know this is wrong, but I have no idea about how to tally the votes by image_id and then order them.
Let me give this a shot to see if I understand your question:
SELECT i.*,(SELECT COUNT(*) FROM _votes WHERE i.id = image_id) AS total_votes, (SELECT count(*) from _votes where i.id = image_id and user_id = ?) as voted FROM _images AS i WHERE i.approved = 1