Re: Relational query with path expressions
From: David BL <davidbl_at_iinet.net.au>
Date: Tue, 7 Apr 2009 22:40:59 -0700 (PDT)
Message-ID: <8b270ef1-6dec-44b0-9b9d-085fdcf6857c_at_u8g2000yqn.googlegroups.com>
Date: Tue, 7 Apr 2009 22:40:59 -0700 (PDT)
Message-ID: <8b270ef1-6dec-44b0-9b9d-085fdcf6857c_at_u8g2000yqn.googlegroups.com>
On Apr 8, 12:02 pm, David BL <davi..._at_iinet.net.au> wrote:
>
> G(x,y) = { (x,y) | exists y in {x}.f }
>
Oops - It doesn't make sense for y to be bound in that sub-expression, so this should have been
G(x,y) = { (x,y) | y in {x}.f }
Note BTW that this notation is quite sloppy because within the setbuilder notation x,y are bound to tuples rather than representing names of attributes from relations input to f or output from f respectively. Received on Wed Apr 08 2009 - 07:40:59 CEST