Grant Fritchey, SQL Server MVP, works for Redgate Software as a Product Advocate. He is the author of the books SQL Server Execution Plans (Simple-Talk) and SQL Server Query Performance Tuning (Apress).
Statistics, Row Counts, Execution Plans, and Query Tuning
Row counts are the primary factor for choices made by the query optimizer. This session explores how row counts affects query performance.
It’s fairly well known that the query optimizer is what creates execution plans. Lots of people are aware that execution plans are the thing that makes queries run fast, or slow. What seems to be less well known is just how vital the number of rows that the optimizer thinks may be returned by any given query is the primary factor driving the choices that the optimizer makes. This session focuses on how the row counts for queries are arrived at and how those row counts impact the choices made by the optimizer and, ultimately, the performance on your system. With the knowledge you gain from this session, you will make superior choices in writing T-SQL, creating indexes and maintaining your statistics. This leads to a better performing system. All thanks to counting the number of rows.