MySQL SUM function

Question

I'm trying to get the sum of a column.

My Schema is as below...

scheme screen shot

I'd like to get the SUM of 'bill'.

I have the following...

   <?php
   $uid = $_SESSION['oauth_id'];
   $query = mysql_query("SELECT * FROM `users`, `income`, `outgoings` WHERE users.oauth_uid = '$uid' and income.user_id = '$uid' and outgoings.user_id = '$uid'") or die(mysql_error());
   $result = mysql_fetch_array($query);
   ?>

   Outgoings = <?php echo $result["SUM(total)"];

I'm not receiving any output, however. Can anybody see where I'm going wrong? There's definitely data in my table.

Why are you bringing the world to you? do you use everything you get? else you could only do SELECT sum(bill) FROM users. — Tamer Shlash
– Tamer Shlash, Commented Apr 12, 2012 at 21:30
Im using everything yes, im new to PHP, is this bad practice? — Liam
– Liam, Commented Apr 12, 2012 at 21:31

user672118 · Accepted Answer · 2012-04-12 21:31:01Z

1

The SUM function must be used when deciding what to return from the select. Like so.

   SELECT SUM(`bill`) FROM `users`, `income`, `outgoings` WHERE users.oauth_uid = '$uid' and income.user_id = '$uid' and outgoings.user_id = '$uid'

answered Apr 12, 2012 at 21:31

user672118

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Comments

Leven · Accepted Answer · 2012-04-12 21:41:02Z

1

Try this if you don't want to do a SUM() query as already proposed by others:

<?php
$sum = 0;
while ($row = mysql_fetch_array($query)) {
    $sum += $row['bill'];
}
?>
Outgoings = <?php echo $sum; ?>

But remember that you will need this if you want to reuse the same $query resultset:

<?php
     mysql_data_seek($query , 0);
?>

edited Apr 12, 2012 at 21:41

answered Apr 12, 2012 at 21:35

Leven

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Comments

thekaveman · Accepted Answer · 2012-04-12 21:31:47Z

0

Why not just query for the SUM directly? Like:

   <?php
       $uid = $_SESSION['oauth_id'];
       $sum = mysql_query("SELECT SUM(`bill`) FROM `users` WHERE users.oauth_uid = '$uid'") or die(mysql_error());
   ?>

answered Apr 12, 2012 at 21:31

thekaveman

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Comments

Tamer Shlash · Accepted Answer · 2012-04-12 21:31:53Z

0

This query will get you the sum:

SELECT sum(bill) FROM `the_table`

answered Apr 12, 2012 at 21:31

Tamer Shlash

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