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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 (view raw or flat)
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

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Next:From: Jasen BettsDate: 2010-03-05 21:27:02
Subject: Re: are primary keys always 'needed'
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Subject: WHERE AND JOIN STATEMENTS

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