As you can see the numbers indicate the relationship between each node. All left values greater than 6 and right values less than 11 are descendants of 6-11 (i.e Id: 3 Amanda).Now If you want to extract out the 2-6 sub-tree for Amanda. What SQL query you will write

SELECT * FROM employee WHERE left_val BETWEEN 6 and 11 ORDER BY left_val ASC;