"... the aggregate functions (SUM, AVG, etc) ... simply egnore any nulls in their argument (except for COUNT(*)) ... if the argument to such a function happens to evaluate to an empty set, the functions all return null (except for COUNT, which returns zero." This from page 222-3,_A Guide to the SQL Standard_, Third Edition, Date C.J. and Hugh Darwen, 1993 Addison Wesley.
So - do we have agreement that NULL's should be ignored in functions that act on aggregates?
To recap: * NULL values cause functions such as ST_UNION to return NULL* This is counter to postgresql's built in aggregates, such as avg/max/min, which ignore the NULL values
I think PostGis should change to match the postgresql semantics. Charlie
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