SQL の join について
SELECT <item-list> FROM table_a A INNER JOIN table_b B ON A.Key = B.Key
SELECT <item-list> FROM table_a A LEFT JOIN table_b B ON A.Key = B.Key
SELECT <item-list> FROM table_a A LEFT JOIN table_b B ON A.Key = B.Key WHERE B.Key IS NULL
SELECT <item-list> FROM table_a A RIGHT JOIN table_b B ON A.Key = B.Key
SELECT <item-list> FROM table_a A RIGHT JOIN table_b B ON A.Key = B.Key WHERE A.Key IS NULL
SELECT <item-list> FROM table_a A FULL OUTER JOIN table_b B ON A.Key = B.Key
SELECT <item-list> FROM table_a A FULL OUTER JOIN table_b B ON A.Key = B.Key WHERE A.Key IS NULL OR B.Key IS NULL