The select null + 0
is not the same as the select sum(a) from a statement. Something equivalent would be select sum(a) where a in (select null as a union select 1 as a) In other words: As far as I understand it, sum() sums up all non null values. In statement you have only one value, which happens to be null which in return adds up to null. In your other statement you have one non null value and sum returns the sum of this one value which is 1. Detlef -----Ursprungliche Nachricht----- Von: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Auftrag von Jean-Christian Imbeault Gesendet: Montag, 14. Juli 2003 07:42 An: [EMAIL PROTECTED] Betreff: [GENERAL] select null + 0 question Why is it that "select null + 1" gives null but "select sum(a) from table" where there are null entries returns an integer? Shouldn't the sum() and "+" operators behave the same? TAL=# select null + 0; ?column? ---------- (1 row) TAL=# select * from a; a --- 1 (3 rows) TAL=# select sum(a) from a; sum ----- 1 (1 row) Thanks, Jean-Christian Imbeault ---------------------------(end of broadcast)--------------------------- TIP 8: explain analyze is your friend ---------------------------(end of broadcast)--------------------------- TIP 7: don't forget to increase your free space map settings
