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SQL Workshop - Selecting columns without including a non-aggregate column in the group by clause

Thinking in terms of sets and set operations can be difficult at first but after a while you discover that you can do things without needed to drop down to procedural approaches.

This scenario requires us to be members of a hospital's Dietary Department and with the end of the year approaching we are assigned the task of estimating the amount of money needed for next year’s resource shopping, to keep the patients fed for the coming twelve months.

So we need to find the sum of the mean amount spent on the resources/raw material (vegetables, fruit, meat etc) grouped by Account Category (i.e. the account that serves for fruit) and Account Id (actual account number) used for their shopping, and use that as the basis for our new season’s budget estimate.

When a request for, say, fruit comes in, we translate that request into the amount of money consumed using a formula based on the fruit’s dynamically updated Mean Value, the Quantity of the request and a Ratio.

When the unit of measurement is 'PIECES' then our formula is :
Amount = Mean Value x Quantity x Ratio

while when the unit of measurement is a ‘KGR’ then the formula becomes:
Amount = Mean Value x Quantity / Ratio

The nature and meaning of the two formulae isn't as important as the fact that they vary according to the value of the Unit field.


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