PHP: summation needed inside of a loop

Question

The student is back. Thanks for you help an patience ;)

I'm using a foreach loop like this:

foreach ($value as $val)
{
//coming from database, from a select query:
$points = $row['points'];  

//now I want to update another database table:  
 $sql = "update user set totalpoints=".$points." where userid=".$uid." ";

//but by doing this, table user is updated with the value of $points in the last iterarion 

}

What do I have to do to update my table with the summation of $points and not with the value of the last iteration?

Thanks again

Do you mean iterate over all rows, sum all the points values, and insert a new row with the total? — William
– William, Commented Feb 22, 2011 at 16:34
SQL has a SUM() function that you can use. It will be faster than querying each row in PHP. — Kai
– Kai, Commented Feb 22, 2011 at 16:36

Felix Kling · Accepted Answer · 2011-02-22 16:33:57Z

3

Not 100% sure but it seems you want:

$sum = 0;

foreach ($value as $val) {
    $sum += $row['points'];  
}

$sql = "update user set totalpoints=".$sum." where userid=".$uid;

answered Feb 22, 2011 at 16:33

Felix Kling

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Gaurav · Accepted Answer · 2011-02-22 16:33:55Z

2

$points = 0;
while ($row = mysq_fetch_array()) // from where you are getting row
{
//coming from database, from a select query:
$points += $row['points'];  

}


//now I want to update another database table:  
 $sql = "update user set totalpoints=".$points." where userid=".$uid." ";

answered Feb 22, 2011 at 16:33

Gaurav

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Elwhis · Accepted Answer · 2011-02-22 16:36:50Z

1

You should do it all in one query

I suppose your original query was something like SELECT * FROM matches WHERE userid='$uid' (whatever) so instead do something like UPDATE user SET totalpoints=(SELECT SUM(points) FROM matches WHERE userid='$uid' GROUP BY userid) WHERE userid='$uid' (Probably it would not fit your exact problem but I hope you get the idea)

answered Feb 22, 2011 at 16:36

Elwhis

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