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I have now rehosted on www.sql.kiwi . You'll find pretty much everything I've ever written there, whether it was originally publishe...

This article was originally published on 𝕏. I was asked recently why Halloween Protection was needed for data modification statements tha...

This article was originally published on 𝕏. SQL Server provides a way to select any one row from a group of rows, provided you write the...

This article was originally published on 𝕏. Background Since SQL Server indexed views don’t allow MIN or MAX aggregates, I recently fo...

This article was originally published on 𝕏. Introduction Update execution plans are not something the T-SQL statement writer has much co...

This article was originally published on 𝕏. Introduction Microsoft encourages us not to use the datetime data type: Avoid using date...

Parallel Index Building Execution Plan SQL Server doesn't support parallel modifications to a b-tree index. That might sound surprising....

Erik Darling ( @erikdarlingdata ) shared an interesting SQL Server execution plan with me recently. The demo script is at the end of this ar...

Setting a Fixed Size for Transaction Log VLFs The documentation has this to say about virtual log file (VLF) sizes: ...

Why Batch Mode Sort Spills Are So Slow Batch mode sorting was added to SQL Server in the 2016 release under compatib...

Fast Key Optimization for Row Mode Sorts SQL Server row-mode sorts generally use a custom implementation of the well-kn...

Importing a File in Batches There are a million ways to import data into SQL Server. Most of the time, we want to inges...

Reducing Contention on the NESTING_TRANSACTION_FULL latch Each additional worker thread in a parallel execution plan ex...

More Consistent Execution Plan Timings in SQL Server 2022 The updated showplan schema shipped with SSMS 19 preview 2 c...

Be Careful with LOBs and OPTION (RECOMPILE) It sometimes makes sense to add OPTION (RECOMPILE) to a query. Typically ...

Empty Parallel Zones An empty parallel zone is an area of the plan bounded by exchanges (or the leaf level) containing...

Incorrect Results with Parallel Eager Spools and Batch Mode You might have noticed a warning at the top of the release ...

sql_handle and the SQL Server batch text hash This article describes the structure of a sql_handle and shows how the...

Closest Match with Sort Rewinds In When Do SQL Server Sorts Rewind? I described how most sorts can only rewind when th...

SQL Server 2019 Aggregate Splitting The SQL Server 2019 query optimizer has a new trick available to improve the perfor...

A bug with Halloween Protection and the OUTPUT Clause Background The OUTPUT clause can be used to return results fro...

How MAXDOP Really Works A few days ago I ran a Twitter poll: The most popular answer gets highlighted by Twitter at ...

Pulling Group By Above a Join One of the transformations available to the SQL Server query optimizer is pulling a logic...

Batch Mode Bitmap Demos This is a companion post to my main article Batch Mode Bitmaps in SQL Server . This post provid...

Apply versus Nested Loops Join SQL is a declarative language. We use SQL to write a logical query specification that d...