Question

I have a table with id column. ids are in ascending order but not necessarily consecutive. For example: 1, 2, 3, 5, 6, 10, 11, 12

I need to find the next “free” id, i.e. max(id) + 1 (or 1 if the table is empty).

Currently I’m doing this in PHP like this:

function get_free_id($con) {
    $sql = "SELECT MAX(id) AS last_id FROM Table";
    $last_id_query = mysql_query($sql, $con);
    $last_id_result = mysql_fetch_array($last_id_query);
    $last_id = $last_id_result['last_id'];  
    return ($last_id == NULL) ? 1 : ($last_id + 1);
}

I have a feeling that this function is “too long” for this simple task and that this can be done much simpler.

Am I right ? How ?

Answer 1

There is no guaranteed way.
So, you shouldn’t do it that way.

Create a record first, get autogenerated id and then use it where you wanted it.