What is difference between INNER join and OUTER join

This is the best and simplest way to understand joins:

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INNER JOIN: Returns all rows when there is at least one match in BOTH tables

LEFT JOIN: Return all rows from the left table, and the matched rows from the right table

RIGHT JOIN: Return all rows from the right table, and the matched rows from the left table

FULL JOIN: Return all rows when there is a match in ONE of the tables

Inner join - An inner join using either of the equivalent queries gives the intersection of the two tables, i.e. the two rows they have in common.
Left outer join - A left outer join will give all rows in A, plus any common rows in B.
Full outer join - A full outer join will give you the union of A and B, i.e. All the rows in A and all the rows in B. If something in A doesn't have a corresponding datum in B, then the B portion is null, and vice versa. check this