sum gives different answer - Mailing list pgsql-sql

From Chairudin Sentosa
Subject sum gives different answer
Date
Msg-id 36E9213D.151B90E1@prima.net.id
Whole thread Raw
List pgsql-sql
Hi all,

I have two SQL statements that I expect to give (0 rows) as output.
However the first one with 'sum' does not do that.
Why the first SQL statement gives (1 row) and empty?
While the second SQL statement can give (0 row).
I am using postgresql 6.4.2.

First
------
select pin, sum(duration) from tablename where date(start_time)=
(select date 'today') group by pin;

pin|sum
---+---
   |
(1 row)


Second
------
select pin, duration from tablename where date(start_time)=
(select date 'today') group by pin;

pin|duration
---+--------
(0 rows)

Could anyone tell me why, please?

Regards
Chai




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