On 21/08/2010 07:25, b@*stripped* wrote:
> Hello,
>
> For simplicity's sake, let's say I have three fields, A, B and C, all
> of which are integers. I'd like the value of C to be equal to A less B
> (A-B). Is there a way I can perform this calculation? I'm guessing it
> would happen when I INSERT a row and specify the values for A and B.
> Feel free to direct me to the fine manual I should have read.
Given two variables, $a and $b:
INSERT INTO mytable SET A = $a, B = $b, C = $a - $b
or
INSERT INTO mytable (A, B, C) VALUES ($a, $b, $a - $b)
or, if you've previously inserted A and B:
UPDATE mytable SET C = A - B
http://dev.mysql.com/doc/refman/5.1/en/numeric-functions.html
Simples :-)
Mark