How do I add data from two tables in mySQL and PHP?

Question

I have a table with two fields, named credithour and gradepoint.

I want to add the data from each row of credithour with gradepoint.

My code :

$totalcredithour = 0;                           
$GPA = "SELECT * FROM $dept_stu_id WHERE sessionyear = '$sessionyear'" or die (mysql_error());
$resultGPA = mysql_query($GPA);
while($data = mysql_fetch_array($resultGPA))
{ 
    $credithour = "$data[credithour]";
    $gradepoint = "$data[gradepoint]";
    echo $totalcredithour += $credithour;   
}

What am I doing wrong?

It added data, but showing the first credit hour also besides result. Suppose, here i entered two data 3 and 5. When I run this code it echo 38. Which means "3+5=8" and 1st credithour = "3".

I tried to edit your question, but it wasn't very clear to begin with. Let me know if I missed anything. — George Stocker
– George Stocker, Commented Nov 15, 2011 at 21:20
i want to retrieve the data from two column, and add each row of data from those column separately. That is i try to doing. — webrider
– webrider, Commented Nov 15, 2011 at 21:31

Manuel Fernández · Accepted Answer · 2011-11-15 21:29:04Z

1

Actually other answer are wrong, you're doing or die(mysql_error()); next to a string, that's not right.

Your code should be like this..

$totalcredithour = 0;                           
$GPA = "SELECT * FROM `".$dept_stu_id."` WHERE sessionyear = `".$sessionyear."` ";
$resultGPA = mysql_query($GPA) or die(mysql_error());
while($data = mysql_fetch_array($resultGPA, MYSQL_ASSOC))
{ 
    $credithour = $data['credithour'];
    $gradepoint = $data['gradepoint'];

    echo $totalcredithour += $credithour; //Make sure `$totalcredithot` isn't null/doesn't exist.
}

answered Nov 15, 2011 at 21:29

Manuel Fernández

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4 Comments

webrider Over a year ago

Still it doesn't working. Yes, "$totalcredithour" is exist and null.

Manuel Fernández Over a year ago

Weird, make sure those columns exists. Also, change echo $totalcredithour += $credithour; to echo $credithour;. So we can check if it's returning null.

webrider Over a year ago

yeah, I have already change that and returning same result. I agree, its weird. I have just edited my post, see that please. Thnx

webrider Over a year ago

I got it. Thank you for replying.

rogerlsmith · Accepted Answer · 2011-11-15 21:13:53Z

0

try something like this in your while loop:

$credithour = $data['credithour'];
$gradepoint = $data['gradepoint'];

answered Nov 15, 2011 at 21:13

rogerlsmith

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2 Comments

rogerlsmith Over a year ago

is your table called $dept_stu_id? it might just be dept_stu_id - the $ designates a php variable.

webrider Over a year ago

Nope, "$dept_stu_id" is a posted variable, which i used as a table name. It isn't a related about this problem dear.

Seder · Accepted Answer · 2011-11-15 22:47:19Z

0

Try it like this

I have edited the answer and added the floatval function

$totalcredithour = 0;                           
  $GPA = "SELECT * FROM `".$dept_stu_id."` WHERE sessionyear = '".$sessionyear."'" or die (mysql_error());
 $resultGPA = mysql_query($GPA);
while($data = mysql_fetch_array($resultGPA))
{ 
$credithour = $data['credithour'];
$gradepoint = $data['gradepoint'];
echo $totalcredithour += floatval($credithour);   
 }

edited Nov 15, 2011 at 22:47

answered Nov 15, 2011 at 21:20

Seder

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1 Comment

webrider Over a year ago

The related data are retrieve successfully, but problem is they don't add. :(

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