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Estimating Row Counts without Statistics

Matthew McGiffen dives into rules of thumb:

I find this is a question that comes up again and agan. What estimate for the number of rows returned does SQL Server use if you’re selecting from a column where there are no statistics available?

There are a few different algorithms used depending on how you’re querying the table. In this post we’ll look at where we have a predicate looking for a fixed value.

Read on for a few examples, noting that this specifically relates to tables and not things like table-valued parameters.