只插入一次MySQL或更新（如果存在）。此处ticket_id是唯一键，但数据不会插入也不会更新。
if(isset($_POST['A1'])){
$seat_no = $_POST['A1'];
$sql_2 = "INSERT INTO ticket_details (ticket_id,".$seat_no.") VALUES('".$ticket_id."','".$ticket_status."') ON DUPLICATE KEY UPDATE ticket_details SET ".$seat_no." = '".$ticket_status."' WHERE ticket_id = '".$ticket_id."'";
mysql_query($sql_2);
}
if(isset($_POST['A2'])) {
$seat_no = $_POST['A2'];
$sql_2 = "INSERT INTO ticket_details (ticket_id,".$seat_no.") VALUES('".$ticket_id."','".$ticket_status."') ON DUPLICATE KEY UPDATE ticket_details SET ".$seat_no." = '".$ticket_status."' WHERE ticket_id = '".$ticket_id."'";
mysql_query($sql_2);
}
if(isset($_POST['A3'])){
$seat_no = $_POST['A3'];
$sql_2 = "INSERT INTO ticket_details (ticket_id,".$seat_no.") VALUES('".$ticket_id."','".$ticket_status."') ON DUPLICATE KEY UPDATE ticket_details SET ".$seat_no." = '".$ticket_status."' WHERE ticket_id = '".$ticket_id."'";
mysql_query($sql_2);
}
**这里我按照this Answer **
解决了上述代码if(isset($_POST['A1'])){
$seat_no = $_POST['A1'];
$sql = "INSERT INTO ticket_details (ticket_id,".$seat_no.") VALUES('".$ticket_id."','".$ticket_status."') ON DUPLICATE KEY UPDATE ".$seat_no." = '".$ticket_status."' ";
$res = mysql_query($sql);
}
if(isset($_POST['A2'])) {
$seat_no = $_POST['A2'];
$sql = "INSERT INTO ticket_details (ticket_id,".$seat_no.") VALUES('".$ticket_id."','".$ticket_status."') ON DUPLICATE KEY UPDATE ".$seat_no." = '".$ticket_status."' ";
$res = mysql_query($sql);
}
if(isset($_POST['A3'])){
$seat_no = $_POST['A3'];
$sql = "INSERT INTO ticket_details (ticket_id,".$seat_no.") VALUES('".$ticket_id."','".$ticket_status."') ON DUPLICATE KEY UPDATE ".$seat_no." = '".$ticket_status."' ";
$res = mysql_query($sql);
}