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This column shows the number of of rows in the access table. It may appear when the Operator name is: Table scan, Index seek, or Clustered index seek. Table cardinality should be used in conjunction with the value of Returned row column. Returned rows shows how many rows were returned after applying all the filter predicates for the selected operation. It allows calculating filtering ratio and assessing the potential of using an index. Let's assume: Operation name is Table scan, Table cardinality is 1000000, and Returned rows is 50. It means that SQL Server sequentially scans a 1000000-row table while only 50 rows were qualified after applying relevant filter predicates. Normally an index may help when the filter ratio (Returned rows / Table cardinality) is less than 1%. You may view filter predicates applied by an Operation by hovering on the Operation and then clicking the More properties link in the presented tool tip.

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