On Aug 31, 2010, at 11:56 PM, Thom Brown wrote: >>> The first form of aggregate expression invokes the aggregate across all >>> input rows for which the given expression(s) yield non-null values. >>> (Actually, it is up to the aggregate function whether to ignore null values >>> or not — but all the standard ones do.) >> >> -- >> http://developer.postgresql.org/pgdocs/postgres/sql-expressions.html#SYNTAX-AGGREGATES >> >> That, however, is not true of array_agg(): >> >> try=# CREATE TABLE foo(id int); >> CREATE TABLE >> try=# INSERT INTO foo values(1), (2), (NULL), (3); >> INSERT 0 4 >> try=# select array_agg(id) from foo; >> array_agg >> ────────────── >> {1,2,NULL,3} >> (1 row) >> >> So are the docs right, or is array_agg() right? > > I think it might be both. array_agg doesn't return NULL, it returns > an array which contains NULL.
No, string_agg() doesn't work this way, for example: select string_agg(id::text, ',') from foo; string_agg ──────────── 1,2,3 (1 row) Note that it's not: select string_agg(id::text, ',') from foo; string_agg ──────────── 1,2,,3 (1 row) Best, David -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
