Add up weights of selected items

[dachshund]

Is it possible to add up a bunch of selected rows?

 

For example, something like this:

 

$sql = "SELECT (and add up) weight FROM store WHERE id LIKE $id" (there are multiple $id's)

 

Obviously that isn't the answer - but hopefully it gives an idea of what I'm after.

 

Thanks

 

Jack

[Drummin]

You would use SUM(weight) in your query.

$sql = "SELECT SUM(weight) FROM store WHERE id LIKE $id"

[dachshund]

thanks, and what about if some some rows needed to be included twice. for example if it needed to add the weight of row 1,1,2 and 4?

[Drummin]

Are you talking about different table fields?  Or the same "weight" field?  If it's the same field then you will get the sum using the same as posted above.  If you need several column fields then get the sum for each and add them together.

[dachshund]

it's the same field, so for the above example it would need to be

 

(weight of id 1 x 2) + weight of id 2 + weight of id 4

 

 

[Drummin]

Give it a try.  SUM(weight) should add up the weight of the queried rows.

[dachshund]

this is what i've tried but it's not quite working

 

<?php
				$basket = $_SESSION['basket'];
				if ($basket) {
				$items = explode(',',$basket);
				$contents = array();
				foreach ($items as $item) {
				$contents[$item] = (isset($contents[$item])) ? $contents[$item] + 1 : 1;
				}
				foreach ($contents as $id=>$qty) {
				$totalweight = mysql_query("SELECT SUM(weight) FROM store WHERE id LIKE '$id'");
				echo $totalweight;
				}
				}
				?>

[dachshund]

ok I worked out SUM, but it just echoed out the weight of that item, and didn't times it by the quantity or add all the different items together

[dachshund]

i worked it out, it's:

 

$itemweight = $rows['weight'] * $qty;

$totalweight += $rows['weight'] * $qty;

[kicken]

Better to use one query rather than in a loop like you did.

 

$ids = array_keys($contents);
$sql = 'SELECT id, SUM(weight) as weight FROM store WHERE id IN ('.implode(',', $ids).') GROUP BY id';
$res = mysql_query($sql);
$weights = array();
while ($row=mysql_fetch_assoc($res)){
   $weights[$row['id']] = $row['weight'];
}

$totalweight=0;
foreach ($contents as $id=>$qty){ 
  $totalweight += $weights[$id] * $qty;
}