Get result from SQL Query

Question

I've got a MySQL query based on a database of ship information, this includes a field ship_name and the key ship_id .

I've written a query which uses the current_ship_id of the page, and finds the next ship based on the alphabetical list of ship_names .

This all works fine, HOWEVER, I'm trying to create a link using the below code in the 'IF' statement.

header("Location: shipinfo.php?ship_id=$next_ship_id"); 

What I don't know how to do is define the variable next_ship_id . I tried the line:

$next_ship_id = ($ship_id);

In theory, I want to get the result of the query $sql (of which I know there is only one result) and find it's ship_id .

How do I do that please?

$sql = "    SELECT ship_infomation.ship_id
              FROM   ship_infomation
        INNER JOIN (
                  SELECT ship_name 
                    FROM   ship_infomation
                   WHERE  ship_id = $current_ship_id
                   ) As current_ship
                ON ship_infomation.ship_name < current_ship.ship_name
          ORDER BY ship_infomation.ship_name ASC
             LIMIT 1";

// echo "<br /><br />$sql<br /><br />";
$ships = mysql_query($sql, $ships) or die(mysql_error());
$row_ships = mysql_fetch_assoc($ships);
$totalRows_ships = mysql_num_rows($ships);
$next_ship_id = ($ship_id);
if ($totalRows_ships = 1)
{
    header("Location: shipinfo.php?ship_id=$next_ship_id");
}
else
{
    // remain on current page  
}

Answer 1

For the next ship use:

SELECT ship_id 
  FROM ship_infomation 
 WHERE ship_id = (SELECT min(ship_id) 
                    FROM ship_infomation 
                   WHERE ship_id > $current_ship_id) 
 LIMIT 1

For the previous ship use:

SELECT ship_id 
  FROM ship_infomation 
 WHERE ship_id = (SELECT max(ship_id) 
                    FROM ship_infomation 
                   WHERE ship_id < $current_ship_id) 
 LIMIT 1

And at your code change this:

$ships = mysql_query($sql, $ships) or die(mysql_error());
$row_ships = mysql_fetch_assoc($ships);
$totalRows_ships = mysql_num_rows($ships);
$next_ship_id = ($ship_id);
if ($totalRows_ships = 1)
{
    header("Location: shipinfo.php?ship_id=$next_ship_id");
}
else
{
    // remain on current page  
}

To this:

$ships = mysql_query($sql, $ships) or die(mysql_error());
$row = mysql_fetch_assoc($ships);
$totalRows_ships = mysql_num_rows($ships);
if ($totalRows_ships = 1)
{
    header("Location: shipinfo.php?ship_id=" . $row['ship_id']);
}
else
{
    // remain on current page  
}

For the next and previous, on your code:

$go = isset($_GET['go']) ? $_GET['go'] : 'next';
if ($go == 'next')
    $sql = "SELECT ship_id FROM ship_infomation WHERE ship_id = (SELECT min(ship_id) FROM ship_infomation WHERE ship_id > ". mysql_real_escape_string($current_ship_id) . ") LIMIT 1";
else
    $sql = "SELECT ship_id FROM ship_infomation WHERE ship_id = (SELECT max(ship_id) FROM ship_infomation WHERE ship_id < ". mysql_real_escape_string($current_ship_id) . ") LIMIT 1";

And on your URL have it like this for the next ship:

http://mysite.com/ships.php?current_ship_id=15&go=next

And like this for the previous:

http://mysite.com/ships.php?current_ship_id=15&go=previous

If the go is not specified it will go to the previous ship by default.

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There is no more support for mysql_* functions, they are officially deprecated , no longer maintained and will be removed in the future. You should update your code with PDO or MySQLi to ensure the functionality of your project in the future.