Continuing his series on row goals, Paul White explains how they can impact certain types of semi joins, and how you can spot these effects in showplan and trace flag output.
Paul White provides some great information about row goals, explaining why they're important to understand when examining why the query optimizer made a certain choice.
Aaron Bertrand acknowledges that DISTINCT and GROUP BY are usually interchangeable, but shows there are cases where one performs better than the other.
Aaron Bertrand (@AaronBertrand) walks through several potential causes for different plans and/or performance for the same database on two "identical" servers.
Paul White (@SQL_Kiwi) demonstrates performance tuning a SQL Server execution plan as a whole, instead of honing in too narrowly on individual operators.