SQL TutorialLesson 30Free preview

SQL Full Join

This lesson is part of SQL · All levels

Summary

FULL OUTER JOIN returns all the rows from the left and right tables; the unmatched section is filled in. Unfortunately MySQL does not support FULL JOIN directly so it must be simulated by combining LEFT JOIN and RIGHT JOIN using UNION. PostgreSQL and SQL Server fully support this command.

Key points

FULL JOIN returns all the second row of the table with NULL for the unpaired.
MySQL does not support FULL OUTER JOIN; simulate with LEFT JOIN UNION RIGHT JOIN.
UNION is used to combine both results while removing duplicates.
FULL JOIN is useful for checking the completeness of the relationship between tables.
The INNER JOIN is just a slice of the full join result.

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