From: Brian Dunning (brianbriandunning.com)
Date: Fri Sep 05 2008 - 17:41:48 CDT

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I'm trying to calculate glycemic index of all food items eaten in a
day with a single SELECT. The problem is the calculation for glycemic
index of each item requires a total of all items' carbs. It's like a
circular reference. Here's what I'm trying:

        SELECT
                sum(fooditems.carb * mealitems.quantity) as sumcarbs,
                sum(fooditems.gi * ((fooditems.carb * mealitems.quantity) /
sumcarbs)),
                sum(fooditems.gl * mealitems.quantity),
                sum(fooditems.cal * mealitems.quantity)
        FROM meals
        INNER JOIN mealitems ON meals.meal_id = mealitems.meal_id
        INNER JOIN fooditems ON mealitems.fooditem_id = fooditems.fooditem_id
        WHERE meals.user_id = '$user_id' AND meals.date = '$meal_date'";

It replies "Unknown column 'sumcarbs' in 'field list'". See what I'm
trying to do? Is there a way to do this?

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