13
votes
3answers
341 views

What is the correct result for this query?

I came across this puzzle in the comments here CREATE TABLE r (b INT); SELECT 1 FROM r HAVING 1=1; SQL Server and PostgreSQL return 1 row. MySQL and Oracle return zero rows. Which is correct? ...
15
votes
3answers
2k views

Why does ANSI SQL define SUM(no rows) as NULL?

The ANSI SQL standard defines (chapter 6.5, set function specification) the following behaviour for aggregate functions on empty result sets: COUNT(...) = 0 AVG(...) = NULL MIN(...) = NULL MAX(...) = ...