joins and indexes -- a=b or b=a?
| От | will trillich |
|---|---|
| Тема | joins and indexes -- a=b or b=a? |
| Дата | |
| Msg-id | 20010328170111.B16380@mail.serensoft.com обсуждение исходный текст |
| Ответы |
Re: joins and indexes -- a=b or b=a?
|
| Список | 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@serensoft.com
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