primary key increase not orderly - php

Question

i have a list of card names and a php file inserting card. When i inserted one card and deleted it in the database then inserted again. The primary key increase after the card delete. For example:
Card number 1
Card number 2
Card number 3 --> if i delete this value and inserte again the primary key is 4 not 3 how to fix that problem ?
Here is my code
<?php
// this file show card name and picture
include("connect.inc");
$connect=mysqli_connect($host,$username,$password,$dbname) or die ("can't connect to server");
$query="SELECT * FROM dragon ";
$result=mysqli_query($connect,$query) or die("can't execute query");
echo $_SESSION['count'];
echo "<hr/>";
while($row=mysqli_fetch_assoc($result))
{
extract($row);
echo $type."<br/>";
echo $CardName."/";
echo $Description;
echo "<br/>";
echo "<a href='../dragon/{$picture}' border='0'> <img src='../dragon/{$picture}' border='0' width='300' height='300'/></a>";
echo "<hr/>";
}
?>
this file shows the insert form
<?php
$labels=array("type"=>"type",
"CardName"=>"Card Name",
"Description"=>"Description",
"atk"=>"Attack",
"def"=>"Defend",
"picture"=>"picture");
echo "<form action='InsertCard.php' method='POST'>";
echo "<h2>Insert new card </h2>";
foreach($labels as $keys =>$values)
{
echo "$values <input type='text' name='$keys'/><br/>";
}
echo "<input type='submit' value='insert new cards'/>";
echo "<input type='submit' name='return' value='return'/>";
echo "</form>";
?>
this file handle the inserted file
<?php
$labels=array("type"=>"type",
"CardName"=>"Card Name",
"Description"=>"Description",
"atk"=>"Attack",
"def"=>"Defend",
"picture"=>"picture");
if(#isset($_POST['return']))
{
header("Location:ShowCatalog.php");
}
include("connect.inc");
$connect=mysqli_connect($host,$username,$password,$dbname) or die("can't connect to server");
foreach($_POST as $keys =>$values)
{
if(empty($values))
{
if($keys=='type' or $keys=='CardName' or $keys=='Description' or $keys=='picture')
{
$empty_values[]=$keys;
}
}
else
{
if($keys=='type')
{
if(!preg_match("/^[A-Za-z -]{4,15}$/",$values))
{
$invalid_data[]=$keys;
}
}
elseif($keys=='CardName')
{
if(!preg_match("/^[A-Za-z -]{4,30}$/",$values))
{
$invalid_data[]=$keys;
}
}
elseif($keys=='Description')
{
if(!preg_match("/^[A-Za-z., -]{4,255}$/",$values))
{
$invalid_data[]=$keys;
}
}
elseif($keys=="atk" or $keys=="def")
{
if(!preg_match("/^[0-9]{3,5}$/",$values))
{
$invalid_data[]=$keys;
}
}
elseif($keys=='picture')
{
if(!preg_match("/^[A-Za-z -]{4,30}(.jpg)$/",$values))
{
$invalid_data[]=$keys;
}
}
/*else
{
$clean_data[$keys]=trim(strip_tags($values));
}*/
}
}
if(#sizeof($empty_values)>0 or #sizeof($invalid_data)>0)
{
if(#sizeof($empty_values)>0)
{
$join=join(", ",$empty_values);
$msg="You forgot to input: $join<br/>";
echo $msg;
}
if(#sizeof($invalid_data)>0)
{
$join=join(", ",$invalid_data);
$msg="Invalid data: $join";
echo $msg;
}
echo "<form action='$_SERVER[PHP_SELF]' method='POST'>";
echo "<h2>Insert new card </h2>";
foreach($labels as $keys =>$values)
{
echo "$values <input type='text' name='$keys'/><br/>";
}
echo "<input type='submit' value='insert new cards'/>";
echo "<input type='submit' name='return' value='return'/>";
echo "</form>";
exit();
}
foreach($_POST as $keys =>$values)
{
$queried_data[$keys]=mysqli_real_escape_string($connect,trim(strip_tags($values)));
}
$check_existence="SELECT CardName FROM dragon WHERE CardName=";
foreach($queried_data as $keys =>$values)
{
if($keys=="CardName")
{
$check_existence.="'".$values."'";
}
}
$checking_result=mysqli_query($connect,$check_existence)or die("can't execute query ".mysqli_error($connect));
if(mysqli_affected_rows($connect)>0)
{
echo "card is already existed !";
include("ShowForm.php");
exit();
}
else
{
$query="INSERT INTO dragon(";
foreach($queried_data as $keys =>$values)
{
$query.=$keys.",";
}
$query.=")";
$query=preg_replace("/\,\)/",")",$query);
$query.="VALUES(";
foreach($queried_data as $keys =>$values)
{
if($keys=="type" or $keys=="CardName" or $keys=="Description")
{
$values=ucfirst($values);
}
if($keys=="atk" or $keys=="def")
{
if(empty($values))
{
$values='n/a';
}
}
$query.="'".$values."',";
}
$query.=")";
$query=preg_replace("/\,\)/",")",$query);
$result=mysqli_query($connect,$query);
echo "card is inserted !";
}
?>

Answer 1

That is expected behaviour, in other words, that's now AI works. Instead of counting on the ID's being sequential, you should keep track of this by yourself in case you need it. When you have done an insert with mysqli, you can fetch the "insert id" after the query has been done, if you need it for reference later.
For more information on getting insert id see:
http://www.php.net/manual/en/mysqli.insert-id.php

Answer 2

This is not a problem. When using autoincrement primary keys, the key assigned to your input is the lowest positive value that has not been assigned yet. This is useful in many ways. For example, you have another table with a foreign key. If your design is bad, you may delete a row from this table and remain with an orphan foreign key. This is a easy detectable error, but if when you insert another row, it gets the key of the deleted row, then yor foreign key will point to other data. This error is very hard to detect. So, the problem is not how keys are assigned, but your expectations. You might consider asking what are you trying to achieve, in order to get an useful answer for your work.

Answer 3

I see you didn't post any code relating to the delete query, so if you are using a delete in sql manually use the following code.
ALTER TABLE dragon AUTO_INCREMENT = 1
this will reset auto incrementing, and sql will insert the next highest integer.
see https://stackoverflow.com/a/8923132/2401804