On Mon, Oct 13, 2014 at 2:05 PM, <mich...@aplaypowered.com> wrote: > case when sum( column1 ) = 0 > then 0 > else round( sum( price > * hours > / column1 ), 2 )
> I would expect that the else part would never be evaluated. > Documentation only describes that this happens for immediates. I explained this behavior in the Stack Overflow answer, it is caused by way aggregates are evaluated in a SELECT (or HAVING) clause. Our documentation should be clearer about the fact that all aggregates are evaluated strictly before their surrounding SELECT expressions, the attached documentation patch adds a note about this to the "general processing of SELECT" explanation. I also created a section "Implementation Notes" in the "Conditional Expressions" chapter to explain this behavior, since conditionals is where this behavior is most visible. This similarly affects the HAVING clause: db=# select sum(1/i) from unnest(array[0])i having min(i)>0; ERROR: division by zero Regards, Marti
0001-doc-Clarify-evaluation-order-of-aggregates-wrt-condi.patch
Description: binary/octet-stream
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