About

Cardinality is the second measure that Query Plan Estimator use to estimate a execution plan.

It represents the number of rows in a row set that the Optimizer expects to come back.

Here, the row set can be :

• a base table,
• a view,
• or the result of a join or GROUP BY operator.

We can find it in for instance in the Autotrace Output where it represent the estimated number of rows that will flow out of a given execution plan step.

Articles Related

Documentation / Reference

• How do I know if the cardinality estimates in a plan are accurate?