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From:David Lerer Date:August 2 2011 6:52pm
Subject:RE: Which is better
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Hard to tell. It depends on the cardinality of tables' id (I assume the
IDs are not unique in each of the tables). David.

-----Original Message-----
From: Shawn Green (MySQL) [mailto:shawn.l.green@stripped] 
Sent: Tuesday, August 02, 2011 2:47 PM
To: Adarsh Sharma
Cc: mysql@stripped
Subject: Re: Which is better

On 8/2/2011 02:41, Adarsh Sharma wrote:
> Dear all,
>
> Just want to know which join is better for querying data faster.
>
> I have 2 tables A ( 70 GB ) & B ( 7 MB )
>
> A has 10 columns & B has 3 columns.Indexes exist on both tables's ids.
>
> select p.* from table A p, B q where p.id=q.id
>
> or
>
> select p.* from table B q , A p where q.id=p.id
>
>
> Thanks
>

There is no difference in performance. The optimizer will change the 
sequence it uses to read the tables according to its own rules.

If you had used STRAIGHT JOIN to force a particular execution path, the 
it would normally be faster to read the smaller table first.

-- 
Shawn Green
MySQL Principal Technical Support Engineer
Oracle USA, Inc. - Hardware and Software, Engineered to Work Together.
Office: Blountville, TN

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Thread
Which is betterAdarsh Sharma2 Aug
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