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13
votes
3answers
356 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? ...
7
votes
1answer
582 views

Is the optimisation fence behaviour of a CTE (WITH query) specified in the SQL:2008 standard? If so, where?

I see frequent references to WITH queries (common table expressions, or CTEs) acting as an optimisation fence, where the server isn't permitted to push filters down into the CTE queries, pull common ...
18
votes
3answers
3k 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(...) = ...
1
vote
2answers
2k views

MySQL case sensitivity for table names

Why is it that different platforms (linux vs windows) does not support the same naming conventions? I'm stunned by the fact that the documentation uses file names as an excuse for this. Yes, windows ...