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Re: WHERE AND JOIN STATEMENTS

From: Tim Landscheidt <tim(at)tim-landscheidt(dot)de>
To: pgsql-novice(at)postgresql(dot)org
Subject: Re: WHERE AND JOIN STATEMENTS
Date: 2010-03-06 01:20:06
Message-ID: m3eijygsah.fsf@passepartout.tim-landscheidt.de (view raw or flat)
Thread:
Lists: pgsql-novice
Jure Kobal <j(dot)kobal(at)gmx(dot)com> wrote:

>> 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.

> 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.

Another disadvantage of the non-JOIN syntax is that you need
to be more careful if you add more conditions with OR.

Tim


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