Php mysql SUM of 1 field from multiple records in different table

Question

I have a script that gets an employees holiday entitlement from their current record in the holiday_entitlement table.

This entitlement figure is then used for each holiday request in the database to be subtracted from.

For example: entitlement days = 27

holiday request days = 2 >>>> entitlement days left = 25

holiday request days = 4 >>>> entitlement days left = 21

holiday request days = 1 >>>> entitlement days left = 20 and so on....

In my script the entitlement days left is $remainder

The bit i am struggling with is to be able to save this $remainder to holiday_entitlement table everytime a request is approved OR work out in SQL the original entitlement figure minus all the requests for that employee, that academic year and if it was approved.

   <?php
    $is_business_result = mysql_query('SELECT * FROM holiday_entitlement WHERE employee = \'' . $username . '\' AND academic_year = \'' . $acyear . '\' ');

    if($is_business = mysql_fetch_array($is_business_result)) {
    echo'<div style="float:left; width:400px;">';

    echo'<table width="100%">
    <tr>
    <td><strong>Name:</strong></td>
    <td>'.$is_business['employee'].'</td>
    </tr>
    <tr>
    <td><strong>Entitlement:</strong></td>
    <td>'.$is_business['new_entitlement'].' '.$is_business['units'].'</td>
    </tr>
    <tr>
    <td><strong>Department / Division:</strong></td>
    <td>'.$is_business['division'].'</td>
    </tr>
    <tr>
    <td><strong>Line Manager:</strong></td>
    <td>'.$is_business['line_manager'].'</td>
    </tr>
    </table>';

    echo'</div>';





    echo'<table class="dataTable" id="business_days_table" cellpadding="2" cellspacing="2" width="100%">
    <thead>
    <th>Start Date</th>
    <th>End Date</th>
    <th>Days to be taken</th>
    <th>Days remaining</th>
    </thead>';

    echo '<tr>';

    echo '<td>-</td>';
    echo '<td>-</td>';
    echo '<td>-</td>';
    echo '<td>'.$is_business['new_entitlement'].'</td>';

    echo '</tr>';


    $input = $is_business['new_entitlement'];
    }

    else {echo 'You currently dont have a record for this academic year. ';}


    $requests_result = mysql_query('SELECT * FROM requests WHERE employee = \'' . $username . '\' AND approved = 1 AND academic_year = \'' . $acyear . '\' ORDER BY start_date ASC');

    $remainder = 0;

    while($requests = mysql_fetch_array($requests_result)) {

    $start_date = new DateTime($requests['start_date']);
    $end_date = new DateTime($requests['end_date']);

    $timestamp_start_date = $start_date->getTimestamp();
    $timestamp_end_date = $end_date->getTimestamp();

    $formatted_start_date = date("d M Y", $timestamp_start_date);           
    $formatted_end_date = date("d M Y", $timestamp_end_date);   

    $remainder = ($remainder == 0) ? $input : $remainder;
    $out = $remainder - $requests['days'];
    if($out < 0){
          break;
    }
    $remainder = $out;


    echo'<tr>';
    echo'<td>'.$formatted_start_date.'</td>';
    echo'<td>'.$formatted_end_date.'</td>';
    echo'<td>'.$requests['days'].'</td>';
    echo'<td>'.$remainder.'</td>';
    echo'</tr>';
    }

    echo'</table>';

    ?>

Answer 1

work out in SQL the original entitlement figure minus all the requests for that employee, that academic year and if it was approved

should be this:

select new_entitlement-(select sum(days) from requests where employee="sashn" and academic_year=2012 and approved=1) from holiday_entitlement where employee="sashn";

or as update:

update holiday_entitlement set new_entitlement=27-(select sum(days) from requests where employee="sashn" and academic_year=2012 and approved=1) where employee="sashn" and academic_year=2012;