PHP数据库中的下一个ID

Question

I need php next id, Ex: i have this id's in database: 10, 11, 15, 19, 31,32,34 .....

$img_id=$_GET[img_id]; // to get image id from browser
$row['id']; // to get id from database

How can I use php $i++ and check if id is set in database? And ignore empty id .

because i want to put next image bottom.while some images was deleted!!

Thank you

Answer 1

From what I understand of your question, you have rows in your database which ids are not consecutive (1, 3, 13, 16, etc), and you wish to access those rows by searching with consecutive numbers from a loop as possible ids?

for($i=0; $i<100; $i++)
{
    $query = 'SELECT * FROM `table` WHERE `id` = ' . $i;
    $result = mysql_query($query);
    if(mysql_num_rows($result) > 0)
    {
        echo 'This id exists in the table: ' . $id . '<br />';
    }
}

100 here acts as a potential number, but it should achieve what you need. There's a ton of solutions that you can apply to your problem, but that would be the most straight forward I think of with the question you're asking.

Answer 2

It's quite unclear what you are trying to say. But I will give it a shot.

I think what you mean is you have deleted some records from the table and it does not continue from last MAX(id) in the next insert. For that you could try:

As @col mentioned below, never use this in production, just your testing environment. Once a record is deleted sequence is lost.

mysql_query("ALTER TABLE `table_name` AUTO_INCREMENT = 1");

What this does is that if you have a table named images with the maximum id of say 99 and you deleted this image. Next image you enter will have the id=100 . So ids will now look something like 97,98,100 . This will force MySQL to continue from MAX(id) + 1 , so it looks 97,98,99 .

Also a handy function to get the last insert id from php:

$last_id = mysql_insert_id();

Now $last_id will have the last AUTO_INCREMENT value from database.

Hope this helps.