Part of theSQL Server 2022 blog series.
Cardinality estimation (CE) is a process used by the query optimizer to estimate the number of rows returned by a query or sub-part of a query. These estimates rely on two underlying things: statistics about the data and a set of assumptionsknown as the model. The model determines how we interpret statistics and data coming from various sub expressions, and so, for any given set of statistics, different models will arrive at different cardinality estimates.
SQL Server 2022
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Until SQL Server 2022, CE could