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12
votes
3answers
270 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? ...
12
votes
3answers
852 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(...) = ...
4
votes
1answer
164 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 ...
3
votes
1answer
162 views
ANSI/ISO plans for LIMIT standardization?
Are there currently plans to standardize one best way of limiting the number of results returned by a query?
The stack overflow question at Is there an ANSI SQL alternative to the MYSQL LIMIT ...
2
votes
1answer
88 views
SQL ISO Standard for group concatenation
Is there an operator in the latest standard SQL:2011 (or earlier) that will handle group concatenation the likes of which we currently have to resort to these tricks for?
GROUP_CONCAT in MySQL
FOR ...
1
vote
2answers
271 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 ...
