"updating" the values in a row using replace

[mccwd]

in my script the user can either add or update an entry, the add part works fine, but the update part doesent.
here is code:

$add_status = "insert into personal_notes values ('', $master_id, now(), now(),'$_POST[note]','$_POST[project_status]','$_POST[complete_bydate]','$_POST[cost]','$_POST[url]')";
//checks to see if creating or editing an entry
 if ($_GET[master_id] != "") {
if ($_POST[project_status]) {

	$add_status = "replace into personal_notes (master_id,date_added,date_modified,project_status) values ($master_id, now(), now(),'$_POST[project_status]')";
mysql_query($add_status) or die(mysql_error());
}
//there is one of these if statments for $_POST[note]','$_POST[project_status]','$_POST[complete_bydate]','$_POST[cost]','$_POST[url]
}

the result of this section of code is a new row with the data that is entered (meaning if there is text in the field it is in new row) but if i dont fill in a field i dont want to the column to be left blank in the new row, how can i use the value of the column from the previous entry with the same master id.

im not sure if i gave enough info but any help would be great
ps. if u need more just ask

[Drakla]

The closest you can get to that with a single query would be using an INSERT with the ON DUPLICATE UPDATE clause. You can read up on it here

http://dev.mysql.com/doc/refman/5.0/en/insert-on-duplicate.html

You'd still have to check for input that was blank and then omit that from the query, so you are going to have to construct your query dynamically. The other option is to select the row first, grab it into an array with mysql_fetch_assoc then replace values that aren't blank and then replace that back.

I presume this isn't for public use and you've got magic quotes on, as there no validation or escaping in your code.

[mccwd]

thanx ill try that
no this wont be a public site, im just sorta experimenting and my host has magic_quotes_gpc on so i dont need to worry bout it.
thatx 4 the help