Hash Join Operator
Produced: 04/05/2014 13:56:00
This is the last of the join operators and possibly the most powerful. It is possibly the most common join operator and, for some reason, one of the ones I hear people most saying they’d like to avoid. Personally I wouldn’t agree with that at all… although it does have a few down sides (which I’ll cover later in this post), it’s by far and away the best choice when joining large datasets together and should therefore be welcomed.

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Merge Operator
Produced: 27/04/2014 17:42:00
Continuing with the posts on Join Operators I’m going to move on from the Nested Loop join and give a very brief explanation of the MERGE operator.

To be honest this is one of the join types I actually see the least out of all three. I’m not sure why this is, but that’s my experience. Doesn’t mean it’s a bad join type though as it’s very, very fast when it does appear. But it does have a couple of pre-requisites before SQL will consider it a viable option.

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Nested Loop Operator
Produced: 20/04/2014 17:36:00
Join operators within SQL Server seem to be very misunderstood in general as people are forever telling me that they want a query to use this or that types of operator for the joins in their plan and they will even use hints to force these. Sadly it seems to come from a misunderstanding that certain types are better than others. This is not the case as they are all designed for a reason and each have their speciality.

In this case I’m going to cover a quick overview of the Nested Loop Join… what it is, how it works, and what it’s best suited for.

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