What does FULL OUTER JOIN return?

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Accepted Answer

A FULL OUTER JOIN combines the behavior of LEFT JOIN and RIGHT JOIN. Every row from both tables appears in the result - rows with a match are joined together, and rows without a match appear with NULLs on the side that had no partner. Note that MySQL does not support FULL OUTER JOIN natively - you have to emulate it with UNION of a LEFT JOIN and a RIGHT JOIN.