On Sat, 2012-09-22 at 20:00 -0700, Chris Travers wrote: > On Sat, Sep 22, 2012 at 12:23 AM, Jasen Betts <ja...@xnet.co.nz> > wrote: > On 2012-09-18, Rafal Pietrak <ra...@zorro.isa-geek.com> wrote:
[-------------] > > could be written by user as (3): > > SELECT 1/x AS inverse FROM data WHERE x <> 0 AND > inverse > 20; > > but token/replaced to its form (2) before WHERE evaluation. > > > Macros are confusing: > > select random()*10 as confusion from generate_series(1,10) > where confusion > 5; No dought about that. And as I really cannot tell you if such processing-alias-as-macro (if available) would make me more error prone or not; I deffinitly know, that I often "upsss.." and rewrite an item from SELECT list into the WHERE clause - because as a common sql-user I do forget such nuances. Learning (for good :), that the ".... as <name>" is *not* a "definition of a logical/local short-name for an expression" (e.g. it is, but only within the context of SQL statement evaluation sequence) is really counterintuitive for an sql-user like myself. > > Also you can already do this: > > > CREATE FUNCTION inverse(data) RETURNS NUMERIC LANGUAGE SQL IMMUTABLE > AS $$ > select case when $1.x = 0 then null else 1/$1.x end; > $$; > Hmmm, well. No. This is an overkill to a problem. I'd rather stay with SELECT list item copyed by hand into the WHERE clauses. -R -- Sent via pgsql-general mailing list (pgsql-general@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
