On Sun, Feb 21, 2021 at 5:27 AM Andrew Lamb wrote:
> For what it is worth, my experience with some SQL databases has been the
> opposite -- ordering can and does differ from statement to statement if the
> clause has a GROUP BY but no ORDER BY).
>
Is this a security issue? If the GROUP BY result
For what it is worth, my experience with some SQL databases has been the
opposite -- ordering can and does differ from statement to statement if the
clause has a GROUP BY but no ORDER BY).
As Andy mentioned, the core reason is performance -- as can require
additional computation to ensure the resu
I understand that GROUP BY ought not imply any particular ordering; it's just
that working with other SQL databases, I've come to expect that ordering will
be consistent between multiple runs of the same statement, at least within the
context of a single transaction on a single connection.
I
The SQL standard in general makes no guarantee of the order of resulting
data unless there is an explicit ORDER BY clause.
I would guess that there are two factors in play here:
1. The use of hash-based data structures, as you mention
2. If you have partitioned data then it is processed on multip
When I group by a column in DataFusion SQL, the order of the results is
different every time. For example, "select country from data group by country"
against
https://github.com/Teradata/kylo/blob/master/samples/sample-data/csv/userdata3.csv
might return "Moldova" first one time, and then "Swed
