Re: WHERE AND JOIN STATEMENTS

From: Jure Kobal <j(dot)kobal(at)gmx(dot)com>
To: pgsql-novice(at)postgresql(dot)org
Cc: JORGE MALDONADO <jorgemal1960(at)gmail(dot)com>
Subject: Re: WHERE AND JOIN STATEMENTS
Date: 2010-03-05 19:01:48
Message-ID: 201003052001.48277.j.kobal@gmx.com
Views: Raw Message | Whole Thread | Download mbox | Resend email
Thread:
Lists: pgsql-novice

> What is the advantage (or advantages) of using JOIN instead of WHERE in a
> SELECT statement?
> Is JOIN faster than WHERE?
>
> I have a SELECT statement that involves 7 tables and I am using WHERE to
> relate them and get the result I need but I want to know if there is a
> performance issue if I change to JOIN.
>
> Respectfully,
> Jorge Maldonado
>

When it comes to speed they are both the same (talking about INNER JOIN here).
You can check the query plan and see it's the same for both.
About the advantages of using JOIN. This is my opinion but for many tables
it's easyer to read the query with JOIN then WHERE clause.
A small example:

SELECT *
FROM a
INNER JOIN
b
ON (
a.id = b.aid
)
WHERE a.id = 'value'

SELECT *
FROM a, b
WHERE a.id = b.aid
AND a.id = 'value'

Now with many tables it's a bit easier to see the relations while using JOIN
instead of WHERE and using WHERE only for conditions.

--
Regards,
Jure

In response to

Responses

Browse pgsql-novice by date

  From Date Subject
Next Message Jasen Betts 2010-03-05 21:27:02 Re: are primary keys always 'needed'
Previous Message JORGE MALDONADO 2010-03-05 18:18:40 WHERE AND JOIN STATEMENTS