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Parallel Execution Plans Suck Summary : A deep dive into SQL Server parallelism, and a potential performance problem wi...

Query Optimizer Deep Dive - Part 4 This is the final part in a series of posts based on the content of the Query Optim...

Query Optimizer Deep Dive – Part 3 This is the third in a series of posts based on the content of the Query Optimizer ...

Query Optimizer Deep Dive – Part 2 This is the second in a series of posts based on the content of the Query Optimizer...

Query Optimizer Deep Dive - Part 1 This is the first in a series of posts based on the content of the Query Optimizer ...

Fun with Scalar and Vector Aggregates There are interesting things to be learned from even the simplest queries. For e...

Dynamic Seeks and Hidden Implicit Conversions A LIKE predicate with only a trailing wildcard can usually use an index...

Forcing a Parallel Query Execution Plan This article is for SQL Server developers who have experienced the special kind...

SQL Server Optimizer Bug with JOIN and GROUP BY I came across a SQL Server optimizer bug recently that made me wonder h...

Is Distinct Aggregation Still Considered Harmful? Back in 2008, Marc Friedman of the SQL Server Query Processor Team wr...

Finding the Statistics Used to Compile an Execution Plan In this post, I show you how to determine the statistics objec...

Can a SELECT query cause page splits? The SQL Server documentation has this to say about page splits : When a new row...

SQL Server, Seeks, and Binary Search The following table summarizes the results from my last two articles, Enforcing Un...

Avoiding Uniqueness for Performance In my last post, Enforcing Uniqueness for Performance , I showed how using a unique...

Enforcing Uniqueness for Performance A little while back, I posted a short series on seeks and scans: When is a Seek ...

Join Performance, Implicit Conversions, and Residuals Introduction You probably already know that it’...

Bitmap Magic (or… how SQL Server uses bitmap filters) Question Can a parallel query use less CPU than the same serial...

Undocumented Query Plans: The ANY Aggregate As usual, here’s a sample table: CREATE TABLE #Example ( pk numeri...

Undocumented Query Plans: Equality Comparisons The diagram below shows two data sets, with differences highlighted: T...

How Parallelism Works in SQL Server You might have noticed that January was a quiet blogging month for me. Part of the...

SQL Server Bug: Slow T-SQL Sums and Averages It’s a curious thing about SQL that the SUM or AVG of no items (an empt...

Advanced T-SQL Tuning: Why Internals Knowledge Matters There is much more to query tuning than reducing logical reads a...

I see no LOBs! Is it possible to see LOB (large object) logical reads from STATISTICS IO output on a table with no LO...

Seeking Without Indexes A seek can contain one or more seek predicates , each of which can either identify (at most) on...

So…is it a Seek or a Scan? You might be most familiar with the terms ‘Seek’ and ‘Scan’ from the graphical plans produce...