ORDER BY in INSERT INTO, how is it done?

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ORDER BY in INSERT INTO, how is it done?

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SwePeso SSC-Dedicated Points: 39752 More actions · Answer 1

Chirag, even if there is a clustered index on the table, it doen't mean that records are stored physically in same order.

I know Itzik Ben-Gan has demonstrated this lately.

The index is ordered, yes.

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jcrawf02 SSC-Insane Points: 24198 More actions · Answer 2

Peso (11/13/2008)
Chirag, even if there is a clustered index on the table, it doen't mean that records are stored physically in same order.
I know Itzik Ben-Gan has demonstrated this lately.
The index is ordered, yes.

So, if you build a clustered index, even if the physical order is not in the same order, if I just pull a SELECT with no order by and include the clustered index in the result set, will the default be to order by the clustered index?

Or does it still depend on query optimiser at the moment of execution?

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"stewsterl 80804 (10/16/2009)I guess when you stop and try to understand the solution provided you not only learn, but save yourself some headaches when you need to make any slight changes."

Matt Miller (4) SSC Guru Points: 124210 More actions · Answer 3

jcrawf02 (11/13/2008)
Peso (11/13/2008)
Chirag, even if there is a clustered index on the table, it doen't mean that records are stored physically in same order.
I know Itzik Ben-Gan has demonstrated this lately.
The index is ordered, yes.
So, if you build a clustered index, even if the physical order is not in the same order, if I just pull a SELECT with no order by and include the clustered index in the result set, will the default be to order by the clustered index?
Or does it still depend on query optimiser at the moment of execution?

It's also a factor of how the data is being retrieved. In some ways it oculd be a simple matter of where the heads are when the request comes in, or whether any of this data is already in cache, etc....

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Gail Shaw SSC Guru Points: 1004504 More actions · Answer 4

jcrawf02 (11/13/2008)
So, if you build a clustered index, even if the physical order is not in the same order, if I just pull a SELECT with no order by and include the clustered index in the result set, will the default be to order by the clustered index?

Maybe. Depends on what index the optimiser decides to use and if there's any parallelism involved.

Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability

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jcrawf02 SSC-Insane Points: 24198 More actions · Answer 5

Thanks Gail/Matt - now that I've read this thread, gotta go fix something . . .

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How best to post your question[/url]
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Tally Table:What it is and how it replaces a loop[/url]

"stewsterl 80804 (10/16/2009)I guess when you stop and try to understand the solution provided you not only learn, but save yourself some headaches when you need to make any slight changes."

Gail Shaw SSC Guru Points: 1004504 More actions · Answer 6

jcrawf02 (11/13/2008)
now that I've read this thread, gotta go fix something . . .

😀 :hehe:

Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability

We walk in the dark places no others will enter
We stand on the bridge and no one may pass

Johan Bijnens SSC Guru Points: 135265 More actions · Answer 7

As always ... if you want order, you must use ORDER BY in the final select clause.

However, at insert time, an order by can have some influence, as stated in the other replies above.

Needs it to be said, when using BULK insert, you'd be better off having your data sorted according to the clustering indexes sequence ?

Even it it were to relief sqlservers burden to sort.

Johan

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