Hi,
I'm writing a custom aggregate function whose result depends on the sort order
of a subselect. It isn't clear whether this a good idea and the documentation
on group_concat(X) seems to suggest that the order that rows are processed by
an aggregate function is not guaranteed ("The order of the concatenated
elements is arbitrary." -- http://www.sqlite.org/lang_aggfunc.html).
Given something like this:
SELECT group_concat(name)
FROM (SELECT * FROM table ORDER BY name)
GROUP BY some_id;
I understood the documentation of group_concat() as meaning that even though
there is an ORDER BY in the subselect, the order of the concatenated names is
not guaranteed. If that is the case, it seems logical that the restriction is
only there because the order in which the aggregate function processes each row
is arbitrary. Does anyone know if this is true or is it safe to assume that the
aggregate will access each row in order?
Thank you,
Emmanuel MacCaull
Software Developer
Research In Motion Limited
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