How to calculate two different values from two different row in mysql database by php
<p>Actually I am creating database on wamp server with the help of php. There is some calculation among some fields.This database for is for lab procurement in which every entry is for new file.Every thing is done but the problem is come when I try to insert a new values for a new file but one value is depend on a value of a previous file.
like
A(FILE NO)  B   C   D
1           2   3   4
2           5   5   9(D1+C2)</p>

<p>So how does is it possible? I am new to this language so if there is another way to do this then please tell me.</p>
