Обсуждение: select sum() possible or not ?

Hello,

I'm using PostgreSQL 7.1

I have a table like :

date logon     logoff
---------------------------------
01-01-02 | 12:02:03 | 12:04:23
01-01-02 | 12:05:13 | 12:08:13
01-01-02 | 13:02:03 | 13:04:23
01-01-02 | 14:02:03 | 14:04:23
01-02-02 | 08:59:03 | 09:09:23
........

and I want to do the following select :

select sum(logoff - logon) from online;

but I receive a error that it's not possible to select a aggregate function
sum(time).

Does someone have an idea why, is there a configuration switch which could solve
the problem?

Thanks

Jörg Naumann

On Thu, 14 Mar 2002 joerg.naumann@miele.de wrote:

> Hello,
>
> I'm using PostgreSQL 7.1
>
> I have a table like :
>
> date logon     logoff
> ---------------------------------
> 01-01-02 | 12:02:03 | 12:04:23
> 01-01-02 | 12:05:13 | 12:08:13
> 01-01-02 | 13:02:03 | 13:04:23
> 01-01-02 | 14:02:03 | 14:04:23
> 01-02-02 | 08:59:03 | 09:09:23
> ........
>
> and I want to do the following select :
>
> select sum(logoff - logon) from online;
>
> but I receive a error that it's not possible to select a aggregate function
> sum(time).
>
> Does someone have an idea why, is there a configuration switch which could solve
> the problem?

I'd suggest upgrading to 7.2, it looks like the above works there.
Failing that maybe try a cast to interval? cast((logoff-logon) as
interval)