Filter 2 UNION joined table columns by URL Parameter

_Hi Chaps,

I have some code, which I can't get to work, think I'm missing something somewhere.

I want to access two tables, and filter them by column 'FK_projid', which is in a URL parameter 'id'

$colname_rsJobs = "-1";
if (isset($_GET['id'])) {
  $colname_rsJobs = $_GET['id'];
}
mysql_select_db($database_conndb2, $conndb2);
$query_rsJobs = sprintf("
(
SELECT
tbl_jobs.FK_projid,
tbl_jobs.jobid,
tbl_jobs.jobname,
tbl_jobs.FK_langid,
tbl_languaget.langtname,
tbl_jobs.jobshipped
FROM
tbl_projects
INNER JOIN tbl_jobs
ON tbl_projects.projid=tbl_jobs.FK_projid
INNER JOIN tbl_languaget
ON tbl_languaget.langtid=tbl_jobs.FK_langid
)
UNION
(
SELECT
tbl_jobxml.FK_projid,
tbl_jobxml.jobid,
tbl_jobxml.jobname,
tbl_jobxml.FK_langid,
tbl_languaget.langtname,
tbl_jobxml.jobshipped
FROM
tbl_projects
INNER JOIN tbl_jobxml
ON tbl_projects.projid=tbl_jobxml.FK_projid
INNER JOIN tbl_languaget
ON tbl_languaget.langtid=tbl_jobxml.FK_langid
)
WHERE FK_projid = %s", GetSQLValueString($colname_rsJobs, "int"));

$rsJobs = mysql_query($query_rsJobs, $conndb2) or die(mysql_error());
//$row_rsJobs = mysql_fetch_assoc($rsJobs);
$totalRows_rsJobs = mysql_num_rows($rsJobs);

I get the error:
You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'WHERE FK_projid = 3525' at line 32

3525 is correct, but I don't know what is stopping the code from working...any ideas?