Comments on: SQL SERVER – Quick Note about JOIN – Common Questions and Simple Answers

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By: Raghav

Raghav — Wed, 09 Nov 2011 14:59:54 +0000

Thanks for such a good post.

By: Ramdas

Ramdas — Fri, 07 Oct 2011 13:39:53 +0000

I like the emphasis on using the INNER JOIN clause instead of using a where to join the columns.

By: Kumar Harsh

Kumar Harsh — Wed, 05 Oct 2011 07:25:01 +0000

SELECT t1.*, t2.*
FROM t1 INNER JOIN t2 ON t1.col1 = t2.col1

This is also better because,join type can easily be change.
For example ,I wrote inner join later on i realize it should be left join.
I just have to replace inner with left.

By: pinaldave

pinaldave — Tue, 04 Oct 2011 08:30:34 +0000

Rob – you are 100% correct.

I agree.

The point of the example was just to demonstrate sub query and inner join syntax. Not the actual query – just to give idea.

Usually I use AdventureWorks database to build the real example.

However, your additionally explanation now will remove any further confusion if there is on this subject.

Thanks for taking time – I am so waiting to meet you soon.

Regards,

By: Rob Farley

Rob Farley — Tue, 04 Oct 2011 07:48:27 +0000

Hi Pinal,

In your IN example, the two queries are not logically identical. If you have multiple rows in t2 that match, you will get extra rows appearing in the results of the JOIN option. IN performs a Semi Join here, whereas JOIN will perform an Inner Join. I’m not writing “Inner Join” in capitals because I’m talking about the logical operation, not the keyword.

Hope this helps,

Rob