Checking users options from default - php

Question

I have table:
user_id | song_id| points
--------|----------------
2 | 1 | 0
2 | 2 | 1
2 | 3 | 2
2 | 4 | 3
2 | 5 | 4
And I need to check if the user have changed the points value.
Therefore it should be something like:
while ($row = mysql_fetch_array($query)) {
$userID = $row['user_id'];
$songID = $row['song_id'];
$points = $row['points'];
if($songID-$points==1){
echo $userID."<br>";
}
But this will print out every occasion of userID where the song-id - points=1.
I need to print out only these user_id's that have all the values =1 and the username must echo'd only once.
EDIT:
SELECT DISTINCT user_id WHERE (song_id - points) = 1
This is half way there. This echo's user_ids' where the song_id - points = 1, but if the user is reordered (i use jQuery sortable) the list, then there can be some rows that is "song_id - points = 1".
My script must echo only these user_id-s, where users every song_id - points = 1, not only one

Answer 1

SELECT DISTINCT user_id FROM table WHERE (song_id - points) = 1
After edit:
SELECT table.user_id
FROM table
LEFT JOIN (
SELECT user_id, COUNT(*) AS C FROM table) AS T2
ON table.user_id = T2.user_id
WHERE (table.song_id - table.points) = 1
GROUP BY table.user_id
HAVING COUNT(*) = T2.C

Answer 2

You can first filter the users which has modified point values:
SELECT DISTINCT user_id FROM table
WHERE (song_id - points) != 1
Then you can use fetch the users which doesn't fit the above condition:
SELECT DISTINCT user_id FROM table
WHERE user_id NOT IN (
SELECT DISTINCT user_id FROM table
WHERE (song_id - points) != 1
)
According to your last edit this last SQL statement might work.
You can check a working example.

Answer 3

Here is what you're looking for:
select user_id from (
select user_id, if(song_id - points = 1, 0, 1) flag from t
) as S
group by user_id
having sum(flag) = 0
And here is a working example.
In case I didn't understand the requirements this shows all users who don't even have one row in which song_id - points != 1, i.e, all users who have all rows that match song_id - points = 1
Or maybe, if you prefer a different approach that might be more efficient:
select distinct t1.user_id from t t1
where not exists (
select * from t t2
where t2.song_id - t2.points != 1 and t1.user_id = t2.user_id
)
Here is the working example.

Answer 4

Not sure I understand the why of the situation, but a simple control-break structure will achieve the desired result ...
$old_id = '';
$good = false;
while($row = mysql_fetch_array($query)){
//check to see if we have a new user ...
if($row['user_id'] != $old_id){
//check to see if all values were == 1
if($good){
echo $old_id . '<br />';
}
//re-initialize variables
$good = true;
$old_id = $row['user_id'];
}
//if value != 1, we won't print the user ...
if($row['song_id'] - $row['points'] != 1){
$good = false;
}
}
//final end-of-loop condition ...
if($good){
echo $old_id . '<br />';
}

Answer 5

OK, here's a query that's a lot more simple than the join above:
SELECT user_id, sum(song_id) as song_total, sum(points) as point_total, count(*) AS cnt FROM table GROUP BY user_id
If the difference between song_id and points is 1 for every song, then the difference between the totals will equal the number of rows for that user ... so using this query:
while($row = mysql_fetch_array($query)){
if($row['cnt'] == ($row['song_total'] - $row['point_total'])){
echo $row['user_id'] . '<br />';
}
}