Basic select and delete in MySQL (PDO) - php

Question

I have the following basic query that selects a PIN from a table, binds it to a variable, and then deletes it from the table.
$sth = $this->db->query("SELECT available_pins FROM pin_list ORDER BY RAND() LIMIT 0,1 ;");
$pinarray = $sth->fetch();
$this->user_pin = $pinarray->available_pins;
$sth = $this->db->prepare("DELETE FROM pin_list WHERE available_pins = ? LIMIT 0,1");
$sth->execute(array($this->user_pin));
My problem: The PIN is selected and echoes fine, but it does not delete from the table. What am I doing wrong?
Also, how would I best add an if statement to catch an error in each of these two cases?

Answer 1

You have a syntax error in your DELETE syntax. LIMIT does not have an offset argument for DELETE.

Answer 2

When selecting the tuple, expand it to include the PK. After you have tied your attribute to a variable, you may delete the tuple by qualifying the where-clause with the PK.
Here is an example. Alas, the example is written in procedural PHP, I haven't coded OO-php for some time now. Sorry about that. Nonetheless, I think the main idea is conveyed. Please let me know otherwise.
Given that the database looks like this:
CREATE TABLE `pin_list` (
`id` INT( 11 ) NOT NULL AUTO_INCREMENT ,
`available_pins` CHAR( 8 ) NOT NULL ,
`aux` VARCHAR( 14 ) NOT NULL ,
PRIMARY KEY ( `id` )
) ENGINE = MYISAM ;
mysql> select * from pin_list;
+----+----------------+-----+
| id | available_pins | aux |
+----+----------------+-----+
| 1 | 43236543 | f |
| 2 | 43236523 | f |
| 3 | 43266523 | f |
| 4 | 48266523 | f |
| 5 | 48264823 | f |
+----+----------------+-----+
5 rows in set (0.00 sec)
The PHP-script may be written like this:
mysql_connect('mysql_server','user-id','pwd');
mysql_select_db('database-name');
//Select the available pin and its PK.
$query = "SELECT id, available_pins FROM pin_list ORDER BY RAND() LIMIT 0,1";
$rs = mysql_query( $query );
//Select id and available_ping into an array
$pinarray = mysql_fetch_array( $rs );
echo "The pin: " . $pinarray[1]; //Do something with it
//Save the primary key (PK, here: the id-attribute) for use in delete statement
$pk = $pinarray[0];
//Now: delete the pin that you have fetched from the database
echo "DELETE FROM pin_list WHERE id = " . $pk; //echo to debug sql-statements in php.
//Uncomment to delete
//$del_qry = "DELETE FROM pin_list WHERE id = " . $pk;
//mysql_query( $del_qry )