How to Work Around MySQL's Lack of FULL OUTER JOIN Functionality?

MySQL does not natively support FULL OUTER JOIN. This results in a syntax error when attempting to use it.

The Solution: Using UNION

To replicate the behavior of a FULL OUTER JOIN, MySQL requires a workaround using the UNION clause. This combines the results of a LEFT JOIN and a RIGHT JOIN.

Here's how to achieve this:

SELECT airline, airports.icao_code, continent, country, province, city, website 
FROM airlines 
LEFT JOIN airports ON airlines.iaco_code = airports.iaco_code
LEFT JOIN cities ON airports.city_id = cities.city_id
LEFT JOIN provinces ON cities.province_id = provinces.province_id
LEFT JOIN countries ON cities.country_id = countries.country_id
LEFT JOIN continents ON countries.continent_id = continents.continent_id
UNION
SELECT airline, airports.icao_code, continent, country, province, city, website 
FROM airlines 
RIGHT JOIN airports ON airlines.iaco_code = airports.iaco_code
RIGHT JOIN cities ON airports.city_id = cities.city_id
RIGHT JOIN provinces ON cities.province_id = provinces.province_id
RIGHT JOIN countries ON cities.country_id = countries.country_id
RIGHT JOIN continents ON countries.continent_id = continents.continent_id;

This query effectively merges the results of a LEFT JOIN (all rows from the left table, matching rows from the right) and a RIGHT JOIN (all rows from the right table, matching rows from the left), providing the complete set of data as a FULL OUTER JOIN would. Note that duplicates will be removed by the UNION operation. If you need to preserve duplicates, use UNION ALL.

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