Why does MySQL report a syntax error on FULL OUTER JOIN?

There is no FULL OUTER JOIN in MySQL. See 7.2.12. Outer Join Simplification and 12.2.8.1. JOIN Syntax:

You can emulate FULL OUTER JOIN using
UNION (from MySQL 4.0.0 on):

with two tables t1, t2:

SELECT * FROM t1
LEFT JOIN t2 ON t1.id = t2.id
UNION
SELECT * FROM t1
RIGHT JOIN t2 ON t1.id = t2.id

with three tables t1, t2, t3:

SELECT * FROM t1
LEFT JOIN t2 ON t1.id = t2.id
LEFT JOIN t3 ON t2.id = t3.id
UNION
SELECT * FROM t1
RIGHT JOIN t2 ON t1.id = t2.id
LEFT JOIN t3 ON t2.id = t3.id
UNION
SELECT * FROM t1
RIGHT JOIN t2 ON t1.id = t2.id
RIGHT JOIN t3 ON t2.id = t3.id

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