Doing something based on change in query

psycovic23

I've got a database where every row has a location (California, Canada, something like that. BTW, these are pictures, so there's more than one row with the same location). Basically, I want to run a query that pulls out the location and continuously loads it into two variables (if there is a better way, please comment). If the location is different between the two variables, do this. If not do this.

For example, let's say row 1 and 2 have a location of CA. Row 3 has a location of CND.

Row 1 location loads into $temp, row 2 location loads into $temp2. Then it compares $temp and $temp2. If they're the same, don't do anything. Now load row 3 into $temp. Compare $temp2 and $temp. They're different, so do this.

Can anyone help?

kerodeon

You will have to make up some sort of loop, ill have a shot and give you an example, though it will most likely have errors (not tested)


$num_rows = mysql_num_rows(SELECT FROM location)
$countnumber = 0;

do {

// stores temp1
$countnumber = $countnumber+1;
$result = mysql_query("SELECT FROM location WHERE id='$countnumber');
$temp1 = $result;

// stores temp2
$countnumber = $countnumber+1;
$result = mysql_query("SELECT FROM location WHERE id='$countnumber');
$temp2 = $result;

// compares, if different, stops loop
if ($temp1!=$temp2) {$countnumber=$num_rows;$different=1;}

}

if ($different==1)  {
//do whatever u want
}

if u want the loop to keep going, just replace
$countnumber=$num_rows;$different=1;
with
//do whatever u want
and delete the last if function

Hope this helps!

EDIT: fixed error in if function

laserlight

A question though: how do you continue?

Writing code to do what you want with 3 rows is easy, but what about 4 rows?
5 rows?
100 rows?

How does the algorithm progress on?

psycovic23

Originally posted by laserlight
A question though: how do you continue?

Writing code to do what you want with 3 rows is easy, but what about 4 rows?
5 rows?
100 rows?

How does the algorithm progress on?

Well...to be honest, I have no idea how to approach this. If using the two variables isn't going to work...then I really don't know how else to do it. A push in a direction will help greatly😃

laserlight

No, I'm not talking about the implementation, I'm talking about the algorithm.

Do you compare 2 adjacent rows, or consider each pair of rows?

psycovic23

Originally posted by laserlight
No, I'm not talking about the implementation, I'm talking about the algorithm.

Do you compare 2 adjacent rows, or consider each pair of rows?

Just two adjacent rows.

At the moment, this is what I'm trying (note that, because I don't know what I'm doing, it's completely wrong. But what I'm trying to do is still visible😃 )

$result = mysql_query("SELECT idname FROM images");
$groups = mysql_query("SELECT distinct idname FROM images");
while ($row = mysql_fetch_array($result))
	{
	while ($group = mysql_fetch_array($groups))
	$identity[] = $group['idname'];
	$locations[] = $row['idname'];
	if (!in_array($locations, $identity))
		echo "<pre>$locations is equal to $groups2. the groups are the same";
	else
		echo "<pre>$locations doesn't eequal $groups2. the groups aren't the same";
	}

laserlight

Assuming that idname is the location name,

<?php
$query = mysql_query("SELECT idname FROM images");
//deal with first row
$row = mysql_fetch_array($query);
$prev = $row['idname'];
//deal with the rest
while ($row = mysql_fetch_array($query)) {
	if ($row['idname'] != $prev) {
		//do something
	}
	$prev = $row['idname'];
}
?>

psycovic23

Yes! Thank you, laserlight!