[SOLVED] alter a specific field

[vwinstead]

I know this doesn't work because I tried it, but what is the correct format for changing the value of a field for a specific line according to an "id" number:

 

$query = "INSERT INTO contents (body)

VALUES ('$postedValue') WHERE id=0";

 

So far I've only been able to INSERT a whole new line, but I don't want to do that, I want to change the value of the "body" field in the line corresponding to an "id" value of zero.

[flyhoney]

UPDATE 
    contents
SET
    body = '$postedValue'
WHERE 
    id = 0

[Snart]

"UPDATE body SET contents = '$postedValue' WHERE id=0"