PHP Calculate rank from database - php

I got a little problem, I've got a database, in that database are different names, id, and coins. I want to show people their rank, so your rank has to be 1 if you have the most coins, and 78172 as example when your number 78172 with coins.
I know I can do something like this:
SELECT `naam` , `coins`
FROM `gebruikers`
ORDER BY `coins` DESC
But how can I get the rank you are, in PHP :S ?

You can use a loop and a counter. The first row from MySql is going the first rank,I.e first in the list.

I presume you want something like:
1st - John Doe
2nd - Jane Doe
..
..
right?
See: http://www.if-not-true-then-false.com/2010/php-1st-2nd-3rd-4th-5th-6th-php-add-ordinal-number-suffix
Helped me a while ago.

You could use a new varariable
$i = "1";
pe care o poti folosi in structura ta foreach,while,for,repeat si o incrementezi mereu.
and you use it in structures like foreach,while,for,repeat and increment it
$i++;
this is the simplest way

No code samples above... so here it is in PHP
// Your SQL query above, with limits, in this case it starts from the 11th ranking (0 is the starting index) up to the 20th
$start = 10; // 0-based index
$page_size = 10;
$stmt = $pdo->query("SELECT `naam` , `coins` FROM `gebruikers` ORDER BY `coins` DESC LIMIT {$start}, {$page_size}");
$data = $stmt->fetchAll();
// In your template or whatever you use to output
foreach ($data as $rank => $row) {
// array index is 0-based, so add 1 and where you wanted to started to get rank
echo ($rank + 1 + $start) . ": {$row['naam']}<br />";
}
Note: I'm too lazy to put in a prepared statement, but please look it up and use prepared statements.

If you have a session table, you would pull the records from that, then use those values to get the coin values, and sort descending.
If we assume your Session table is sessions(session_id int not null auto_increment, user_id int not null, session_time,...) and we assume that only users who are logged in would have a session value, then your SQL would look something like this: (Note:I am assuming that you also have a user_id column on your gebruikers table)
SELECT g.*
FROM gebruikers as g, sessions as s WHERE s.user_id = g.user_id
ORDER BY g.coins DESC
You would then use a row iterator to loop through the results and display "1", "2", "3", etc. The short version of which would look like
//Connect to database using whatever method you like, I will assume mysql_connect()
$sql = "SELECT g.* FROM gebruikers as g, sessions as s WHERE s.user_id = g.user_id ORDER BY g.coins DESC";
$result = mysql_query($sql,$con); //Where $con is your mysql_connect() variable;
$i = 0;
while($row = mysql_fetch_assoc($result,$con)){
$row['rank'] = $i;
$i++;
//Whatever else you need to do;
}
EDIT
In messing around with a SQLFiddle found at http://sqlfiddle.com/#!2/8faa9/6
I came accross something that works there; I don't know if it will work when given in php, but I figured I would show it to you either way
SET #rank = 0; SELECT *,(#rank := #rank+1) as rank FROM something order by coins DESC
EDIT 2
This works in a php query from a file.
SELECT #rank:=#rank as rank,
g.*
FROM
(SELECT #rank:=0) as z,
gebruikers as g
ORDER BY coins DESC

If you want to get the rank of one specific user, you can do that in mysql directly by counting the number of users that have more coins that the user you want to rank:
SELECT COUNT(*)
FROM `gebruikers`
WHERE `coins` > (SELECT `coins` FROM `gebruikers` WHERE `naam` = :some_name)
(assuming a search by name)
Now the rank will be the count returned + 1.
Or you do SELECT COUNT(*) + 1 in mysql...

Related

Select a fixed number of records from a particular user in a sql result

I have 2 tables - users and articles.
users:
user_id (int)
name (varchar)
articles:
article_id (int)
user_id (int)
title (varchar)
description (text)
In my application I need to display 20 RANDOM articles on a page.
My query is like this:
SELECT a.title
, a.description
, u.name
FROM articles a
JOIN users u
USING (user_id)
ORDER
BY RAND()
LIMIT 20
A user can have any number of articles in the database.
Now the problem is sometimes out of 20 results, there are like 9-10 articles from one single user.
I want those 20 records on the page to not contain more than 3 (or say 4) articles from a particular user.
Can I achieve this through SQL query. I am using PHP and MySQL.
Thanks for your help.
You could try this?
SELECT * FROM
(
SELECT B.* FROM
(
SELECT A.*, ROW_NUMBER() OVER (PARTITION BY A.USER_ID ORDER BY A.R) USER_ROW_NUMBER
FROM
(
SELECT a.title, a.description, u.name, RND() r FROM articles a
INNER JOIN users u USING (user_id)
) A
) B
WHERE B.USER_ROW_NUMBER<=4
) C
ORDER BY RAND() LIMIT 20
Mmm, intresting I don't think this is possible through a pure sql query.
My best idea would be to have an array of the articles that you'll eventually display query the database and use the standard SELECT * FROM Articles ORDER BY RAND() LIMIT 20
The go through them, making sure that you have indeed got 20 articles and no one has breached the rules of 3/4 per user.
Have another array of users to exclude, perhaps using their user id as an index and value of a count.
As you go through add them to your final array, if you find any user that hits you rule add them to the array.
Keep running the random query, excluding users and articles until you hit your desired amount.
Let me try some code (it's been a while since I did php)
$finalArray = [];
$userArray = [];
while(count($finalArray) < 20) {
$query = "SELECT * FROM Articles ";
if(count($finalArray) > 0) {
$query = $query . " WHERE articleID NOT IN(".$finalArray.")";
$query = $query . " AND userID NOT IN (".$userArray.filter(>4).")";
}
$query = $query . " ORDER BY Rand()";
$result = mysql_query($query);
foreach($row = mysql_fetch_array($result)) {
if(in_array($finalArray,$row) == false) {
$finalArray[] = $row;
}
if(in_array($userArray,$row[userId]) == false) {
$userArray[$row[userId]] = 1;
}
else {
$userArray[$row[userId]] = $userArray[$row[userId]] + 1;
}
}

Best way to sum and seperate by date in MYSQL with/witout php

Hi i have such table information:
what i want to do with php with while or just in mysql, is to SUM (time_used) of the rows with status 44 until its reached row with status 55. after that it should begin from start with new summing.
first query should return 37, second 76 (keep in mind it should be universal, for unlimited occurrences of 55 status row)
i thought of a way with time/date filtering and have this:
select sum(time_used) as sumed
from timelog
where start_time > (select end_time from timelog where (status='55')
ORDER BY id DESC LIMIT 1) ORDER BY id DESC
but this works only for last combination of 44 and 55
i know i will need two way filtering( < end_time and > end_time) so it will work for all cases, but cant think of a way to do it in php
can anyone help me?
EDIT:
sqlfiddle whoever want it:
http://sqlfiddle.com/#!2/33820/2/0
There are two ways to do it: Plain SQL or PHP. If you treat thousands of rows, it may be interresting to choose between the two by testing performance.
Plain SQL
select project_id, task_id, user_id, sum(time_used) as time_used,
min(start_time) as start_time, max(end_time) as end_time, max(comment) as comment from
(select t.id, t.project_id, t.task_id, t.user_id, t.time_used,
count(t2.id) as count55, t.start_time, t.end_time, t.comment
from timelog t
left join timelog t2 on t.id>t2.id and t2.status=55 and t.task_id=t2.task_id
group by t.id) as t
group by count55;
I assume here that a task can belong to one user only
SQL and PHP
$link = mysqli_connect( ... );
$query = "select id, project_id, task_id, user_id, time_used, start_time, end_time, status
from timelog order by id";
$result = mysqli_query($link, $query);
$table = array();
$time_used = 0;
$start_sum = true;
$i = 0;
while($row = mysqli_fetch_assoc ($result)){
if($start_sum){
$table[$i] = $row;
$start_sum = false;
} else {
$table[$i]['time_used'] += $row['time_used'];
$table[$i]['end_time'] += $row['end_time'];
}
if($row['state'] == 55){
$i++;
$start_sum = true;
}
}
If two tasks can run in simultaneously, solution 1 will work, but solution 2 will need to be adapted in order to take this in account.
here is my intepretation:
http://sqlfiddle.com/#!2/33820/45
set #n=0;
select project_id, task_id, user_id,sum(time_used) from (
SELECT time_used,project_id, task_id, user_id,
#n:=if(status=55,#n+1,#n),
if(status=55,-1,#n) as grouper FROM timelog
) as t
where grouper>-1
group by grouper;
I'm neither a php nor MySQL programmer, but I can explain the logic you want to follow. You can then code it.
First, query your db and return the results to php.
Next, set two sum variables to 0.
Start looping through your query results. Increment the first sum variable until you reach the first row that has status 55. Once you do, start incrementing the second variable.
The tricky part will be to sort your query by the row number of the table. Here is a link that will help you with that part.

mysql + php: Selecting multiple random results

I've been looking for this for a while but with no success.
I am trying to implement a recomendation bar, for example like in youtube, when you are seeing a video it shows the list or recommended videos on the right.
At this moment I am using this method:
$offset_result = mysql_query( " SELECT FLOOR(RAND() * COUNT(*)) AS `offset` FROM `$tablename` ");
$offset_row = mysql_fetch_object($offset_result );
$offset = $offset_row->offset;
$result_rand = mysql_query( " SELECT * FROM `$tablename` LIMIT $offset, 9 " );
This works fine, but sometimes doesn't show any result, and the problem is also that its not completely random, because it shows for example the first ID as 200, so the next result will be id 201 and then 202 and so.
I would like to know if there is a way to show this 9 randon results, for example 1º result id 500, 2º result id 10, 3º result id 788, etc etc?
Thank you
Not entirely sure this answers what you are looking for, but try:
$result_rand = mysql_query("SELECT * FROM " . $tablename . " ORDER BY RAND() LIMIT 9");
You can use php rand() function to create 5 numbers and save them in an array:
http://php.net/manual/en/function.rand.php
<?php
$rand_array = array();
for($i=1;$i<5;$i++) {
$rand_array[$i] = rand(0,500);
}
?>
and after that create a query with every int with a foreach loop and work with your data.
<?php
foreach ($rand_array as $integer) {
$q = "SELECT * from $tablename WHERE id='$integer';";
}
?>
Does this helps?
First you should use mysqli_ functions instead of mysql_ because the latter is deprecated. Second use order by rand() to get random rows:
$rand_result = mysqli_query( "SELECT * FROM $tablename ORDER BY RAND() LIMIT 9;" );
UNTESTED:
SELECT id, #rownum:=#rownum+1 AS rownum, name
FROM users u,
(SELECT #rownum:=0) r
THis will give a unique number to each row in sequence. Now if you create a temp table with 9 random numbers between 1 and count(*) of your table and JOIN those two together...
Not sure about performance but seems like it might be faster than Rand and order by since I only need 9 random numbers

SQL query construction

I recently created a scoring system where the users are ordered by their points on descending basis. First I used to store ranks in a column of its own. I used to run this loop to update the rank:
$i = 1;
$numberOfRows = mysql_query('SELECT COUNT(`id`) FROM sector0_players');
$scoreboardquery = mysql_query("SELECT * FROM sector0_players ORDER BY points DESC");
while(($row = mysql_fetch_assoc($scoreboardquery)) || $i<=$numberOfRows){
$scoreid = $row['id'];
$mysql_qeury = mysql_query("UPDATE sector0_players SET scoreboard_rank = '$i' WHERE id = '$scoreid'");
$i++;
}
And it was really hard, not to mention slow to actually run this on a huge amount of users.
Instead, I tried to construct a query and ended up with this.
SET #rownum := 0;
SELECT scoreboard_rank, id, points
FROM (
SELECT #rownum := #rownum + 1 AS scoreboard_rank, id, points FROM sector0_players ORDER BY points DESC
)
as result WHERE id = '1';
But, this is just a select statement. Is there anyway I could get around it and change it so that it updates the table just as the loop does?
Please try using the following query :
set #rownum:=0;
update sector0_players set scoreboard_rank=#rownum:=#rownum+1 ORDER BY points DESC;
PHP code can be ,
mysql_query("set #rownum:=0;");
mysql_query("update sector0_players set scoreboard_rank=#rownum:=#rownum+1 ORDER BY points DESC;");
You can try using the RANK function .. I haven't actually executed the SQL, but it should work
UPDATE sector0_players
SET scoreboard_rank =
(
SELECT srank
FROM
(
SELECT id,points, RANK() OVER (ORDER BY points) AS srank
FROM sector0_players T
) D
WHERE D.id = sector0_players.id
AND D.points = sector0_players.points
)

while (mysql_fetch_array) in a while loop

i have this code:
while ($sum<16 || $sum>18){
$totala = 0;
$totalb = 0;
$totalc = 0;
$ranka = mysql_query("SELECT duration FROM table WHERE rank=1 ORDER BY rand() LIMIT 1");
$rankb = mysql_query("SELECT duration FROM table WHERE rank=2 ORDER BY rand() LIMIT 1");
$rankc = mysql_query("SELECT duration FROM table WHERE rank=3 ORDER BY rand() LIMIT 1");
while ($rowa = mysql_fetch_array($ranka)) {
echo $rowa['duration'] . "<br/>";
$totala = $totala + $rowa['duration'];
}
while ($rowb = mysql_fetch_array($rankb)) {
$totalb = $totalb + $rowb['duration'];
}
while ($rowc = mysql_fetch_array($rankc)) {
$totalc = $totalc + $rowc['duration'];
}
$sum=$totala+$totalb+$totalc;
}
echo $sum;
It works fine, But the problem is until "$sum=16" the "echo $rowa['duration']" executes, the question is, is there a away to "echo" only the latest executed code in the "while ($rowa = mysql_fetch_array($ranka))" i this while loop?
Because most of the times returns all the numbers until the "$sum=16"
You are explicitly echoing the $rowa['duration'] in the first inner while loop. If you only want to print the last duration from the $ranka set, simple change the echo to $rowa_duration = $rowa['duration'] then echo it outside the loop.
while ($rowa = mysql_fetch_array($ranka)) {
$rowa_duration = $rowa['duration'];
$totala = $totala + $rowa['duration'];
}
echo $rowa_duration . '<br/>';
What you are doing there is bad on multiple levels. And your english horrid. Well .. practice makes perfect. You could try joining ##php chat room on FreeNode server. That would improve both your english and php skills .. it sure helped me a lot. Anyway ..
The SQL
First of all, to use ORDER BY RAND() is extremely ignorant (at best). As your tables begin the get larger, this operation will make your queries slower. It has n * log2(n) complexity, which means that selecting querying table with 1000 entries will take ~3000 times longer then querying table with 10 entries.
To learn more about it , you should read this blog post, but as for your current queries , the solution would look like:
SELECT duration
FROM table
JOIN (SELECT CEIL(RAND()*(SELECT MAX(id) FROM table)) AS id) as choice
WHERE
table.id >= choice.id
rank = 1
LIMIT 1
This would select random duration from the table.
But since you you are actually selecting data with 3 different ranks ( 1, 2 and 3 ), it would make sense to create a UNION of three queries :
SELECT duration
FROM table
JOIN (SELECT CEIL(RAND()*(SELECT MAX(id) FROM table)) AS id) as choice
WHERE
table.id >= choice.id
rank = 1
LIMIT 1
UNION ALL
SELECT duration
FROM table
JOIN (SELECT CEIL(RAND()*(SELECT MAX(id) FROM table)) AS id) as choice
WHERE
table.id >= choice.id
rank = 2
LIMIT 1
UNION ALL
SELECT duration
FROM table
JOIN (SELECT CEIL(RAND()*(SELECT MAX(id) FROM table)) AS id) as choice
WHERE
table.id >= choice.id
rank = 3
LIMIT 1
Look scary, but it actually will be faster then what you are currently using, and the result will be three entries from duration column.
PHP with SQL
You are still using the old mysql_* functions to access database. This form of API is more then 10 years old and should not be used, when writing new code. The old functions are not maintained (fixed and/or improved ) anymore and even community has begun the process of deprecating said functions.
Instead you should be using either PDO or MySQLi. Which one to use depends on your personal preferences and what is actually available to you. I prefer PDO (because of named parameters and support for other RDBMS), but that's somewhat subjective choice.
Other issue with you php/mysql code is that you seem to pointlessly loop thought items. Your queries have LIMIT 1, which means that there will be only one row. No point in making a loop.
There is potential for endless loop if maximum value for duration is 1. At the start of loop you will have $sum === 15 which fits the first while condition. And at the end that loop you can have $sum === 18 , which satisfies the second loop condition ... and then it is off to the infinity and your SQL server chokes.
And if you are using fractions for duration, then the total value of 3 new results needs to be even smaller. Just over 2. Start with 15.99 , ends with 18.01 (that's additional 2.02 in duration or less the 0.7 per each). Again .. endless loop.
Suggestion
Here is how i would do it:
$pdo = new PDO('mysql:dbname=my_db;host=localhost', 'username', 'password');
$pdo->setAttribute(PDO::ATTR_EMULATE_PREPARES, false);
$sum = 0;
while ( $sum < 16 )
{
$query = 'that LARGE query above';
$statement = $pdo->prepare( $query );
if ( $statement->execute() )
{
$data = $statement->fetchAll( PDO::FETCH_ASSOC );
$sum += $data[0]['duration']+$data[1]['duration']+$data[2]['duration'];
}
}
echo $data[0]['duration'];
This should do what your code did .. or at least, what i assume, was your intentions.

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