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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...

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

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...

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

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 ...

Allocation Order Scans When an execution plan includes a scan of a b-tree index structure, the storage engine may be ab...

Nested Loops Prefetching Nested loops join query plans can be a lot more interesting (and complicated) than is commonly...

Two Partitioning Peculiarities Table partitioning in SQL Server is essentially a way of making multiple physical tables...

The Problem with Window Functions and Views Introduction Since their introduction in SQL Server 2005, window functions...

Execution Plan Analysis: The Mystery Work Table I love SQL Server execution plans. It is often easy to spot the cause o...

Halloween Protection – The Complete Series I have written a four-part series on the Halloween Problem . Some of you wi...

The Halloween Problem – Part 4 The Halloween Problem can have a number of important effects on execution plans. In this...

The Halloween Problem – Part 3 The MERGE statement (introduced in SQL Server 2008) allows us to perform a mixture of ...