Measure the Area of Geographic Polygons

Calculate the Area of a Polygon

Write a MySQL query to calculate the area of polygons stored in the GeoData table using ST_Area.

Solution:

-- Calculate and display the area 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_Area function to calculate the area of the 'area' column (a POLYGON). 
    -- The result is aliased as 'areaSize' for clarity.
    ST_Area(area) AS areaSize

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

Explanation:

• Purpose of the Query:
• The goal is to compute the area (in square units) of the stored polygons.
• This demonstrates the use of ST_Area for spatial measurement.
• Key Components:
• ST_Area(area) : Calculates the area of the polygon.
• AS areaSize : Provides an alias for the calculated value.
• Real-World Application:
• Important for land management, planning, and resource allocation.

Notes:

• The calculated area is dependent on the coordinate system used.

For more Practice: Solve these Related Problems:

• Write a MySQL query to calculate and display the area of each polygon in the "GeoData" table using ST_Area.
• Write a MySQL query to compute the area for polygons in the "MapAreas" table and filter out those with an area less than 5000 square units.
• Write a MySQL query to select the name and area of each region from "Regions" using ST_Area, ordering the results by area in descending order.
• Write a MySQL query to calculate the total area of all polygons in the "LandParcels" table using ST_Area and aggregate functions.

Go to:

• Hands-on MySQL Spatial Data Exercises Home. ↩
• MySQL Exercises Home ↩

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