更新、加入和 WHERE MySQL

Question

I'm currently working on my query. So I have two tables, tbl_room and tbl_reservation. I wanted to do an update query with the following conditions:

Decrement room counter by 1 in tbl_room if:

1. The first and last name of the customer matches the first and last name in the tbl_reservation
2. The tbl_reservation room ID matches with the tbl_room room ID

I'm currently stuck with this:

$result = mysql_query("UPDATE 
  tbl_room 
  JOIN tbl_reservation 
    ON tbl_room.roomID = tbl_reservation.roomID 
    AND tbl_reservation.cus_fname = '$cusFN' 
    AND tbl_reservation.cus_lname = '$cusLN' SET tbl_room.reserve = reserve - 1 ");

These are my tables:

----------
tbl_room
----------
roomID,
room_type,
capacity,
reserve <--- reservation counter


----------
tbl_reservation
----------
reserveID,
cus_fname,
cus_lname,

Answer 1

I already came up with the right query. Yehey! So I moved my query just after the while statement and used this syntax:

$result6 = mysql_query("UPDATE tbl_room
           JOIN tbl_reservation ON tbl_room.roomID=tbl_reservation.roomID
           AND tbl_reservation.cus_fname='$cusFN'
           AND tbl_reservation.cus_lname='$cusLN'
           SET tbl_room.reserve=tbl_room.reserve-1");

Answer 2

Try this...

$sql = "UPDATE `tbl_room`
SET `tbl_room`.`reserve` = `tbl_room`.`reserve` - 1 
WHERE `tbl_room`.`roomID` = `tbl_reservation`.`roomID` 
 AND `tbl_reservation`.`cus_fname` = '$cusFN' 
 AND `tbl_reservation`.`cus_lname` = '$cusLN'";