From: | will trillich <will(at)serensoft(dot)com> |
---|---|
To: | pgsql-general(at)postgresql(dot)org |
Subject: | joins and indexes -- a=b or b=a? |
Date: | 2001-03-28 23:01:11 |
Message-ID: | 20010328170111.B16380@mail.serensoft.com |
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Thread: | |
Lists: | pgsql-general |
if you have a main table on which you're doing a linear scan:
create table person (
id varchar(12), -- handle/id/login
name varchar(30),
gang int4
);
that joins another indexed table:
create table gang (
id serial,
name varchar(30),
primary key(id)
);
is there any significant difference in the following two queries:
select
p.id as handle, p.name as person, g.name as gang
from
person p, gang g
where
PERSON.GANG = GANG.ID
;
-- as opposed to:
select
p.id as handle, p.name as person, g.name as gang
from
person p, gang g
where
GANG.ID = PERSON.GANG
;
the only difference is GANG.ID=PERSON.GANG versus
PERSON.GANG=GANG.ID in the WHERE clause. does it matter?
--
It is always hazardous to ask "Why?" in science, but it is often
interesting to do so just the same.
-- Isaac Asimov, 'The Genetic Code'
will(at)serensoft(dot)com
http://newbieDoc.sourceforge.net/ -- we need your brain!
http://www.dontUthink.com/ -- your brain needs us!
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