Question

I would like to update a row, but I would like to leave unchaged a field when there is not a new value to update the field with.

I know I can write a new query, but my table is quite long and I’m looking for an elegant way to do the job.

Let’s say that part of my long table is the following:

|  id  |   Name   | date_added | date_updated |
-----------------------------------------------
|  1   | Review_1 | 2012-02-10 | 2012-02-20   |

I have a form with a checkbox. I would like that if the user checks the checkbox the field date_updated is updated with the current date. But if the checkbox is not checked the field date_updated if left unchanged.

if (isset($_POST['updated'])) { 
    $updated = [today's date];
}

At the moment my query is this:

mysql_query("UPDATE reviews r, filters f SET 
                                             r.title = '$title', 
                                             r.description = '$description',
                                             r.date_updated = '$updated',
                                             r.link_homepage = '$homepage'
                                             [etc.]
                                             [etc.]

            WHERE r.id = '$id' AND f.id = '$id' ") or die(mysql_error());

Answer 1

You can just leave out the date_updated line if it’s not needed. So:

$updated = '';
if (isset($_POST['updated'])) { 
    $updated = "r.date_updated = NOW(),";
}

and then in the query:

...
r.description = '$description',
$updated
r.link_homepage = '$homepage'
...