From: Daevid Vincent
Date: April 18 2006 2:33am
Subject: How can I use a value computed in my SQL query for further computations?
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Here is a paired down version of a query I want to make. How can I get the
"grandtotal" column? I know about the "HAVING" clause, but that's only going
to be good for weeding out rows I don't want. I just want to do some basic
math here.

SELECT  a.*, 
	DATE_FORMAT(a.created_on,'%m/%d/%y %h:%i:%s %p') AS
created_on_format, 
	DATE_FORMAT(a.timestamp,'%m/%d/%y %h:%i:%s %p') AS timestamp_format,

	(views * ppview) AS totalviews, 
	(clicks * ppclick) AS totalclicks,
	totalviews + totalclicks AS grandtotal
FROM advertisements a;

There has got to be a better way than this (which would be a colossal waste
of computing power to recalculate something that was just done!):

SELECT  a.*, 
	DATE_FORMAT(a.created_on,'%m/%d/%y %h:%i:%s %p') AS
created_on_format, 
	DATE_FORMAT(a.timestamp,'%m/%d/%y %h:%i:%s %p') AS timestamp_format,

	(views * ppview) AS totalviews, 
	(clicks * ppclick) AS totalclicks,
	((views * ppview) + (clicks * ppclick)) AS grandtotal
FROM advertisements a;