How Can I Perform a FULL OUTER JOIN in MySQL?

MySQL Doesn't Support FULL OUTER JOIN: A Solution

Standard SQL's FULL OUTER JOIN isn't directly supported in MySQL. The provided SQL statement will result in a syntax error.

Alternative Approach: Combining LEFT and RIGHT JOINs

To achieve the equivalent of a FULL OUTER JOIN in MySQL, you can combine LEFT JOIN and RIGHT JOIN operations using UNION. This approach effectively merges results from both joins to include all rows from both tables, matching where possible.

Example using UNION:

<code class="language-sql">SELECT * FROM a
LEFT JOIN b ON a.id = b.id
UNION
SELECT * FROM a
RIGHT JOIN b ON a.id = b.id</code>

This query first performs a LEFT JOIN (all rows from the left table, a, and matching rows from the right table, b). Then, a RIGHT JOIN (all rows from the right table, b, and matching rows from the left table, a) is executed. Finally, UNION combines the results, eliminating duplicate rows. This effectively mirrors the functionality of a FULL OUTER JOIN.

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