Calculate database index selectivity: Selectivity = unique_values / total_rows. High selectivity (>0.9) = effective index. Low selectivity (< 0.2) = index often not used. Boolean columns have selectivity ~0.5.
Enter the values for the scenario you are assessing. Calculate database index selectivity: Selectivity = unique_values / total_rows. High selectivity (>0.9) = effective index. Low selectivity (< 0.2) = index often not used. Boolean columns have selectivity ~0.5. Use the index selectivity result to inform your calculation.