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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...

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

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

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

Aggregates and Partitioning The changes in the internal representation of partitioned tables between SQL Server 2005 an...

Working Around Missed Optimizations In my last post , we saw how a query featuring a scalar aggregate could be transfor...

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

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...

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

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...

Row Goals and Grouping You might recall from Inside the Optimizer: Row Goals In Depth that query plans containing a r...

Ranking Function Optimizer Transformations In my last post I showed how SQL Server 2005 and later can use a Segment ...

Partitioning and the Common Subexpression Spool SQL Server 2005 introduced the OVER clause to enable partitioning of...