Michael Toews wrote:
Now, I would like to group a summary of the strings in "sub", but they
must be ordered alphabetically. Here I attempt the SQL:
select commacat(sub), grp from aggr_test group by grp;
However, on my system it will output the "commacat" column as:
"one, two, three";"pom pom"
"two, three, one";"la la"
(notice that the items in the first column are ordered differently,
since the input values were entered in non-alphabetically)
This is where I get confused, since in the aggregate function, I have
specified `SORTOP="<"`, which according to the documentation
(http://www.postgresql.org/docs/8.3/interactive/sql-createaggregate.html)
"must be equivalent to":
SELECT sub FROM aggr_test ORDER BY sub USING <; -- LIMIT 1;
That's for things like min()/max() where you only want the first/last
value of some set. You want all of them.
You could accumulate the values in an array and then sort that with the
final-func that create aggregate supports.
--
Richard Huxton
Archonet Ltd
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