MySQL Index Selectivity Calculator

MySQL Index Selectivity Calculator calculator can be used to determine the selectivity of an index in a MySQL database. Selectivity is the fraction of rows that satisfy a specific condition in a table.

Input Parameters

Calculation Results

Calculation Formula

Selectivity = Total Rows / Matching Rows

Where:
- Total Rows: Total number of rows in the table
- Matching Rows: Number of rows that satisfy the specific condition

MySQL Index Selectivity Calculator Calculator Usage Guide

Learn how to use the MySQL Index Selectivity Calculator calculator and its working principles

How to Use the Calculator

  1. Enter the total number of rows in your table in the "Total Number of Rows in Table" field.
  2. Enter the number of rows that match your specific condition in the "Number of Rows Matching Condition" field.
  3. Click the "Calculate" button to compute the selectivity and see the interpretation.
  4. Use the "Reset" button to clear all fields and start over if needed.

Understanding Selectivity

Selectivity is a measure of how unique the values in a column are. It is calculated as the ratio of the total number of rows to the number of rows that match a specific condition. A selectivity of 1 means all rows match the condition, while a selectivity of 0 means no rows match the condition.

Selectivity is important in database indexing as it helps in optimizing query performance. A highly selective index (low selectivity) is more efficient for queries because it reduces the number of rows that need to be scanned.

Interpreting the Results

  • A selectivity of 1 indicates a non-selective index where all rows match the condition.
  • A selectivity of 0 indicates a highly selective index where no rows match the condition.
  • Selectivity values between 0.1 and 0.9 indicate moderate selectivity.