| From: | Bruce Momjian <maillist(at)candle(dot)pha(dot)pa(dot)us> |
|---|---|
| To: | tgl(at)sss(dot)pgh(dot)pa(dot)us (Tom Lane) |
| Cc: | lockhart(at)alumni(dot)caltech(dot)edu, darcy(at)druid(dot)net, pgsql-hackers(at)postgreSQL(dot)org |
| Subject: | Re: [HACKERS] SUM() and GROUP BY |
| Date: | 1999-01-13 17:43:07 |
| Message-ID: | 199901131743.MAA16352@candle.pha.pa.us |
| Views: | Raw Message | Whole Thread | Download mbox | Resend email |
| Thread: | |
| Lists: | pgsql-hackers |
> I disagree ... the sum of zero items has traditionally been defined as
> zero by any mathematician you care to ask. No logical problems are
> introduced by doing so, and it avoids an unpleasant special case that
> applications would otherwise be forced to deal with. (Example: if
> D'Arcy's tramount column has been declared NOT NULL, then it seems to me
> that his code is entitled to expect to get a non-NULL result from SUM().
> He should not have to cope with a NULL just because the table is empty.)
Informix returns NULL for sum. It returns a zero only for count().
--
Bruce Momjian | http://www.op.net/~candle
maillist(at)candle(dot)pha(dot)pa(dot)us | (610) 853-3000
+ If your life is a hard drive, | 830 Blythe Avenue
+ Christ can be your backup. | Drexel Hill, Pennsylvania 19026
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