An INNER JOIN returns only the rows where the join condition matches in both tables.
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What does a LEFT JOIN return?
A LEFT JOIN keeps every row from the left table, filling right-table columns with NULL where there is no match.
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What does a FULL OUTER JOIN return?
A FULL OUTER JOIN returns all rows from both tables, with NULLs where a side has no match.
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What does a CROSS JOIN produce?
A CROSS JOIN pairs every row of the first table with every row of the second, producing the cartesian product.
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Why does join filtering belong in ON vs WHERE for outer joins?
In an outer join, conditions in ON apply during matching (preserving unmatched outer rows), while a WHERE on the joined table can filter out the NULL-filled rows, effectively turning it into an inner join.