What is the result of a join between table1 and table2?

The result of a join depends on the join type. An INNER JOIN returns only rows where the join condition matches in both tables, producing a set of rows that have matching keys. A LEFT (or LEFT OUTER) JOIN returns all rows from the left table and the matching rows from the right table; unmatched rows from the right table are filled with NULLs. A RIGHT JOIN is the opposite, and a FULL OUTER JOIN returns all rows from both tables, with NULLs where there is no match. For example, if table1 has columns (id, name) and table2 has (id, salary), an INNER JOIN on id will produce rows with id, name, salary only for ids present in both tables. A LEFT JOIN will include all ids from table1, adding salary where available and NULL otherwise.