空值MySQL

Question

What is the best way to handle NULL values in a search form. I want to allow the user to search by 8 different criteria however if they leave a box blank I would like it to return all non null values for that column. I am able to assign a default value if the field is left blank but how can I change accountant to "IS NOT NULL"? Thank you for your time.

    if ($specialty_name == null){
        $specialty_name = 'Accountant';
    }

The SQL looks like this... WHERE specialty_name = 'Accountant'

Answer 1

Something like this:

if ($specialty_name == null) {
    $where = "WHERE specialty_name IS NOT NULL";
} else {
    $where = "WHERE specialty_name = '$specialty_name'";
}