Finding skipped invoices in db

[no_maam]

Hi !
I have a database with invoices. How do i find invoices that are skipped from beeing entered into the db (based on the invoice number )

E.g:
invoice_number | amount | client_id | etc. |

100---------------------|--150----|--128------|------|
101---------------------|--140----|--124------|------|
102---------------------|--150----|--125------|------|
103---------------------|--120----|--128------|------|
105(should be 104)------|--115----|--156------|------|
106---------------------|--150----|--124------|------|
107---------------------|--160----|--121------|------|
How do i detect invoice numbers that have been skipped?(in this case =104=)

thanks!

[devinemke]

$result = mysql_query('SELECT invoice_number FROM invoices ORDER BY invoice_number');
while ($row = mysql_fetch_assoc($result))
{
	extract($row);
	if (isset($last_row))
	{
		$diff = $invoice_number - $last_row;
		if ($diff != 1)
		{
			for ($i = 1; $i < $diff; $i++)
			{
				$missing = $last_row + $i;
				echo 'missing ' . $missing . '<br>';
			}
		}
	}
	$last_row = $invoice_number;
}

[mrhappiness]

SELECT ( f.id -1 )missing_id
FROM fubar f
LEFT  JOIN fubar missing ON f.id -1 = missing.id
WHERE ISNULL( missing.id ) 
ORDER BY missing_id ASC
LIMIT 1, 99999999 

you'll need the LIMIT since (according to your data) you will receive id 99 as missing

but due to this LIMIT the first entry get's skipped