It is useful to verify that all fields are NULL in MYSQL to query data from a database so they can be treated differently from fields with numeric values or text. NULL indicates an unknown value, which is different from a default value, such as 0 or ‘ ‘. You can use the PHP function “is_null” to tell if a returned MYSQL field is NULL or not.
1. Open your PHP source code in a text editor such as Notepad.
2. Use the “mysql_query (query)” function to send a query to the active MYSQL database. For example, “$result = mysql_query (“Select row from Tname”);”.
3. Use the “mysql_fetch_assoc ($result)” function within a “while” loop to fetch rows from the MYSQL result. For example, “while ($row = mysql_fetch_assoc ($result)) “.
4. Use the “is_null (variable)” inside “while” loop to determine if a field of a returned row has a NULL value. For example, if (is_null ($row [“LName”])) {echo “is null”;}} “will print” is null “values for any ” row ” which are NULL.
5. Save the PHP below file and run.
<!DOCTYPE html>
<html>
<body>
<?php
$result = mysql_query ("Select row of Tname");
while ($row = mysql_fetch_assoc ($result))
{
if (is_null ($row ["LName"]))
{echo "is null";}
}
?>
</body>
</html>
