adding up numbers & update database

[ZwartWitVlindertje]

Hey all, I'm using PHP/MySQL & Dreamweaver 8 with Interakt MX Kollektion, and I ran into something I could use some help with. After a lot of googling I finally found out how to add up numbers and show the result.

My question is:
Number 1 + Number 2 = Number 3

What do I do to store 'Number 3' in the DB?

Any help would be very very very welcome. Been going crazy over this for a long time now.

[Newsgroup_User]

Basically you write an update statement that picks up the calculated Number
3 and stores it in the approprate field in the DB.

--
Paul Whitham
Certified Dreamweaver MX2004 Professional
Adobe Community Expert - Dreamweaver

Valleybiz Internet Design
www.valleybiz.net

"ZwartWitVlindertje" <webforumsuser@macromedia.com> wrote in message
news:ef9r2u$gks$1@forums.macromedia.com...
> Hey all, I'm using PHP/MySQL & Dreamweaver 8 with Interakt MX Kollektion,
> and I
> ran into something I could use some help with. After a lot of googling I
> finally found out how to add up numbers and show the result.
>
> My question is:
> Number 1 + Number 2 = Number 3
>
> What do I do to store 'Number 3' in the DB?
>
> Any help would be very very very welcome. Been going crazy over this for a
> long time now.
>

[Newsgroup_User]

ZwartWitVlindertje wrote:
> My question is:
> Number 1 + Number 2 = Number 3
>
> What do I do to store 'Number 3' in the DB?

If numbers 1 and 2 are already stored in the database, you don't need to
store number 3. In fact, you shouldn't. A general principle of databases
is that data should be stored at its basic level, and you should never
store the result of a calculation derived from numbers already stored in
the database.

Why? Let's say your database stores prices, and everything is subject to
10% sales tax. If you create another column for the tax-inclusive price,
you will have to update every single record in the database if the tax
rate goes up to 15%. However, by storing the price on its own, you can
always calculate the tax-inclusive price either in PHP or in your SQL query.

SELECT price * 110 AS tax_inc FROM price_table

--
David Powers
Adobe Community Expert
Author, "Foundation PHP for Dreamweaver 8" (friends of ED)
http://foundationphp.com/

[ZwartWitVlindertje]

Guess I should have explained this, what I want to do is:

Money + Gamecredits = Money (updated)

And the GameCredits should be put back at 0.

I have been trying for so long now, different ways, asked around on other forums and still not working... What would the update statement look like?

$sql=mysql_query ("UPDATE User SET userMoney = userCredits + '$userMoney' WHERE userID = '$userID'");

Something like that? =/

[Newsgroup_User · Accepted solution]

ZwartWitVlindertje wrote:
> $sql=mysql_query ("UPDATE User SET userMoney = userCredits + '$userMoney'
> WHERE userID = '$userID'");
>
> Something like that? =/

No. If you want to add userMoney to userCredits and reset userCredits to
0, it would look like this:

$sql = "UPDATE User SET userMoney = userMoney+userCredits, userCredits =
0 WHERE userID = $userID";
mysql_query($sql);

--
David Powers
Adobe Community Expert
Author, "Foundation PHP for Dreamweaver 8" (friends of ED)
http://foundationphp.com/