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Channel: Query Processor – Paul S. Randal
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Which index will SQL Server use to count all rows

This is a question that came up yesterday on Twitter: will SQL Server always do a table scan to find the result of SELECT COUNT (*) FROM mytable? The answer is no. The query processor will use the...

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Two great blog series on joins and query plan operators

I was doing some research this morning for some query tuning on a client system and I came across a couple of blog series with some excellent posts for those looking to learn more about query plans...

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DBCC CHECKDB performance and computed-column indexes

It’s no secret that DBCC CHECKDB has some performance quirks based on the schema of the database being checked and various kinds of corruptions. I was recently doing some scalability testing of DBCC...

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Reconciling set-based operations with row-by-row iterative processing

Yesterday in class we had a discussion around the conceptual problem of reconciling the fact that SQL Server does set-based operations, but that it does them in query plans that pass single rows around...

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SQLskills SQL101: Query plans based on what’s in memory

As Kimberly blogged about recently, SQLskills is embarking on a new initiative to blog about basic topics, which we’re calling SQL101. We’ll all be blogging about things that we often see done...

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DBCC CHECKDB performance and computed-column indexes

[Edit 2016: The team ‘fixed’ the problem in SQL Server 2016 by skipping consistency checking these indexes unless WITH EXTENDED_LOGICAL_CHECKS is used.] It’s no secret that DBCC CHECKDB has some...

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Reconciling set-based operations with row-by-row iterative processing

Yesterday in class we had a discussion around the conceptual problem of reconciling the fact that SQL Server does set-based operations, but that it does them in query plans that pass single rows around...

View Article

SQLskills SQL101: Query plans based on what’s in memory

As Kimberly blogged about recently, SQLskills is embarking on a new initiative to blog about basic topics, which we’re calling SQL101. We’ll all be blogging about things that we often see done...

View Article

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