Data insert not success when using varchar as primary key? - php

Question

This is my table
CREATE TABLE room (
room_ID VARCHAR(8),
room_name TEXT(50),
room_capacity INT(3),
room_building VARCHAR(20),
room_type VARCHAR(20),
room_desc TEXT(100),
PRIMARY KEY (room_ID)
);
and this is my insert code.
<?php
//Start session
session_start();
//Import connection
include('conn.php');
$room_ID = $_POST["room_ID"];
$room_type = $_POST["room_type"];
$room_name = $_POST["room_name"];
$room_capacity = $_POST["room_capacity"];
$room_building = $_POST["room_building"];
$room_desc = $_POST["room_desc"];
//echo $room_ID;
//echo $room_type;
//echo $room_name;
//echo $room_capacity;
//echo $room_building;
//echo $room_desc;
//Check for duplicate room ID
//if($room_ID != '') {
$qry = "SELECT room_ID FROM room WHERE room_ID = '".$room_ID."'";
$result = mysql_query($qry);
if($result) {
if(mysql_num_rows($result) > 0) {
header("location: duplicateID.php");
exit();
}
#mysql_free_result($result);
}
else {
die("Yang ini lah failed");
}
}
//Create INSERT query
$qry = "INSERT INTO room (room_ID, room_name, room_capacity, room_building, room_type, room_desc)
VALUES('$room_ID', '$room_name', '$room_capacity', '$room_building', '$room_type', '$room_desc')";
$result = #mysql_query($qry);
//Check whether the query was successful or not
if($result) {
header("location: addroomsuccess.php");
exit();
} else {
die("Query failed");
}?>
But the problem is, the process stuck in the first if else. But when i delete those if else, the query still failed. Why did this happen? Is it because im using varchar as the data type for the primary key?

Answer 1

So much wrong with this.
1) If you have a PK you will not get duplicates so your check is pointless.
2) Just insert it. If it fails, you have a duplicate or some other problem. Checking first just narrows the opportunity but it can still go wrong in a multiuser environment.
3) SQL injection - read up on it, understand it at implement SQL that avoids it (parameters).
But to answer your question, not it has nothing to do with VARCHAR as a PK - that's fine if it makes sense. #AlexandreLavoie's advice is not good or relevant (sorry!).