INNER JOIN 3 tabelle

[luca rulvoni]

Salve a tutti,

ho un problema con Inner Join e tre tabelle.

Ho tre tabelle:

democat (categoria)
demosubcat (sottocategoria)
demoarticoli (articoli)

tutte e tre le tabelle hanno in comune il campo idcat.

la mia query che recupera correttamente tramite $_GET il valore $id :


<?php
include ("config.inc.php");
include ("connect.php");
// recupero valore da id pagina
$id = $_GET['id'];

//inserimento dati su tabella
//$query="DELETE FROM democat WHERE idcat='$id'";
/*$query="DELETE democat.*, demosubcat.*, demoarticoli.*
FROM democat INNER JOIN demosubcat, demoarticoli
ON democat.idcat = demosubcat.idcat AND democat.idcat = demoarticoli.idcat
WHERE democat.idcat ='$id'";*/
$query1="SELECT COUNT(*) FROM demosubcat";

$result1 = mysql_query($query1,$db);

$righe = mysql_num_rows($result1);

if ($righe == 0 ) {

$query2="DELETE FROM democat WHERE idcat='$id'";

}
$query2="SELECT COUNT(*) FROM demoarticoli";

$result2 = mysql_query($query2,$db);

$righe2 = mysql_num_rows($result2);

if ($righe2 == 0) {

$query3="DELETE FROM democat, demosubcat USING democat, demosubcat WHERE democat.idcat=demosubcat.idcat AND democat.idcat='$id'";

}else{



$query4="DELETE FROM democat, demosubcat, demoarticoli USING democat, demosubcat, demoarticoli WHERE democat.idcat=demosubcat.idcat AND democat.idcat=demoarticoli.idcat AND democat.idcat='$id'";


/*$query ="DELETE FROM demosubcat, demoarticoli USING demosubcat, demoarticoli WHERE demosubcat.subcat=demoarticoli.subcat AND demosubcat.subcat='$id'";*/

$result3 = mysql_query($query4,$db);

if($result3) {
echo '<script>alert("Categoria eliminata.");
location="eliminacategorie.php";
</script>';


}else{
echo "categoria non eliminata";


}

}
}

?>

Se devo eliminare categoria, subcategoria e articoli associati riesco ad eliminare, ma se desidero soltanto eliminare categoria e subcategoria non posso ...