Duplicate counting

Ji�� N�mec wrote:

Hello all,

I wrote a function which counts price of product from retail price and
discount. It works. But I need to count price with tax of same
product. The best way is to use counted price and add only a tax. I
would like to do by this way:

SELECT count_price(retail, discount) AS price, count_price_tax(price,
tax) FROM foo.

But PostgreSQL reports that "price" column doesn't exist. It doesn't
exist, but is counted by first calling "count_price()" function.

Is there some way how I shouldn't count these prices twice and use
just counted price?

It's not quite clear to me what count_price and count_price_tax are
supposed to do. Does count_price_tax return the equivalent of
price*(1.0+tax) (or maybe price*tax)? If so, one way to do it is to use
a sub-query like this:

SELECT price, count_price_tax(price, tax) FROM (SELECT
count_price(retail, discount) AS price, tax FROM foo) AS bar;

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Aaron Bingham
Application Developer
Cenix BioScience GmbH
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