Обсуждение: BUG #11642: Aggregate Functions like min, max return one row in case of no rows in table

The following bug has been logged on the website:

Bug reference:      11642
Logged by:          Jai Soni
Email address:      jai.soni@elbizsystems.com
PostgreSQL version: 9.3.0
Operating system:   Open Suse Linux 12.1
Description:

Aggregate Functions like min, max return one row in case of no rows in table
it should return 0 rows as it return while using normal field in select
query
below code will re-create the case

# create table dummy(fid integer);

# select * from dummy;
 fid
-----
(0 rows)

# select max(fid) from dummy;
 max
-----

(1 row)

On 10/11/14, 9:31 AM, jai.soni@elbizsystems.com wrote:
> Aggregate Functions like min, max return one row in case of no rows in table
> it should return 0 rows as it return while using normal field in select
> query

According to whom?

This behaviour is well defined in the SQL standard and documented for
example here:
http://www.postgresql.org/docs/9.3/static/sql-select.html#SQL-GROUPBY

"Aggregate functions, if any are used, are computed across all rows
making up each group, producing a separate value for each group (whereas
without GROUP BY, an aggregate produces a single value computed across
all the selected rows)."


.marko