On Wed, Jun 3, 2009 at 9:18 PM, Oliver Kohll - Mailing Lists <oliver.lists@xxxxxxxxxx> wrote:
Hello,
We have a system that allows users to create views containing calculations but divisions by zero are commonly a problem.
An simple example calculation in SQL would be
SELECT cost / pack_size AS unit_cost from products;
Either variable could be null or zero.
I don't think there's a way of returning null or infinity for divisions by zero, rather than causing an error but I'd just like to check - and put in a vote for that functionality!
If not, I will have to get the system to check for any numeric fields in user input calculations and rewrite them similar to
CASE WHEN cost IS NULL THEN null
WHEN pack_size IS NULL THEN null
WHEN cost = 0 THEN null
WHEN pack_size = 0 THEN null
ELSE cost / pack_size
AS unit_cost
I don't want to write new functions, I'd rather keep it in plain SQL.
Putting that in a function is definitely going to be expensive..
You need to take care of only one case here: denominator == 0; rest of the cases will be handled sanely by the database.
CASE WHEN packet_size = 0 THEN null ELSE cost/packet_size END as unit_cost
Best regards,
--
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