"Rui Martins" <Rui.Martins@PDMFC.com> writes:
> Here the context of the word "match" may be misleading us, in this
> conversation.
> I say this, because in my report, the second substring expression, the one
> for RoomSize:
> SUBSTRING( BedNo, '^[[:digit:]]+([a-zA-Z]*)(:[[:digit:]]+)?$' ) AS RoomSize,
> Actually returns an EMPTY String, and not a NULL, for the first 2 test
> cases, which I believe is the correct answer.
What's your point? A zero-length substring is a legal match to that
subexpression ... unlike the third one.
regards, tom lane