Compute the Boundary Length of Polygons

Calculate the Perimeter of a Polygon

Write a MySQL query to calculate the perimeter of polygons in the GeoData table using ST_Perimeter.

Solution:

-- Calculate and display the perimeter of each polygon stored in the 'area' column of the GeoData table.
SELECT 

    -- Select the 'name' column to display the name of the geographic entity.
    name, 

    -- Use the ST_Perimeter function to calculate the perimeter of the 'area' column (a POLYGON). 
    -- The result is aliased as 'perimeter' for clarity.
    ST_Perimeter(area) AS perimeter

-- Retrieve data from the GeoData table.
FROM GeoData;

Explanation:

• Purpose of the Query:
• The goal is to compute the length of the boundary of each polygon.
• This demonstrates the use of ST_Perimeter for measuring spatial boundaries.
• Key Components:
• ST_Perimeter(area) : Computes the perimeter of the polygon.
• AS perimeter : Assigns a name to the resulting measurement.
• Real-World Application:
• Useful for applications requiring boundary measurements, such as property surveys.

Notes:

• Ensure that the spatial reference system supports accurate length calculations.

For more Practice: Solve these Related Problems:

• Write a MySQL query to calculate and display the perimeter of each polygon in the "GeoData" table using ST_Perimeter.
• Write a MySQL query to compute the perimeter for polygons in the "MapAreas" table and sort the results by perimeter length.
• Write a MySQL query to select the name and perimeter of each area from "Regions" using ST_Perimeter, filtering out values below a threshold.
• Write a MySQL query to calculate the cumulative perimeter of all polygons in the "PropertyBoundaries" table using ST_Perimeter and aggregation.

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Previous MySQL Exercise: Calculate the Area of a Polygon.
Next MySQL Exercise: Create a Buffer around a Point.