Adding value from dropdown or textfield to one database field

Please have a look to the attachment to see what im trying to do.
Database field= "Age"
i want that if a user choose date of birth or if he writes his age in text box, the data goes to the fieldname 'Age ' only

how do i do this?

$insert = mysql_query("insert into register (Name,Gender,DOB,Age,TOB,POB) values ('".$_SESSION['Name']."', '".$_SESSION['Gender']."', '".$_SESSION['DateofBirth']."', '".$_SESSION['Age']."', '".$_SESSION['Timeofbirth']."', '".$_SESSION['Placeofbirth']."')

or die("Could not insert data because ".mysql_error());

PHP:

im a newbie to php/mysql
please help!

 

the sql looks ok for me.
r u not seeing the data getting inserted into the 'Age' field?

 

What you are trying to achieve ? You'll need to check it and execute 2 different SQL queries - one if it's empty, second if it's filled in.