如果数据库为空，如何添加数据？

Question

I'm trying to add a number to a column called ID in my database. What should happen is when there no data in the database this script will insert the first line with the ID numbered as 1 but the issue is it's not working.

I think my checking of null data is the issue can one of you help me by pointing out what should I do.

My code

<?php

/**
 * @author SiNUX
 * @copyright 2013
 */

include ('connect.php');

$lastId = mysql_query("SELECT ID FROM poiinfo");

$row = mysql_fetch_array($lastId);

if (is_null($row['ID'])){

    $nId = $row['ID'];
    $nId = 0;
    $nId = $nId++;

    $addId = "INSERT INTO poiinfo(`ID`) VALUES ('$nId')";
    mysql_query($addId);

}else {

    $lId = $row['ID'];
    $lId = $lId + 0;
    $lId++;
}

?>

Answer 1

this query which you are executing

INSERT INTO poiinfo('ID') VALUES ('$nId')

will most likely fail because the columnname was enclosed by single quote. The quote should be reomved or replace it with backtick, eg

INSERT INTO poiinfo(ID) VALUES ('$nId')

or

INSERT INTO poiinfo(`ID`) VALUES ('$nId')

and so the question is, when do I use backtick? It's you are using a name which is on the list of MySQL's reserved keyword,

• MySQL Reserved Keywords List

and lastly, you must pass the variable containing the query in mysql_query()

mysql_query($addId);