SQL Self Join and Tree Checks | Dataford Interview Questions

Explain how you would write SQL to solve a self join problem, and describe how you would determine whether two binary trees are identical.

Use the provided employee and tree-node tables. Return reporting pairs and one comparison result for the two trees.

Output

Reporting rows with result_type, employee_id, manager_id, employee_name, and manager_name, followed by one tree row with trees_identical.
Include employees with a non-null manager who matches another employee.
Order reporting rows by manager_id, then employee_id, followed by the tree result.

employees

Column	Type	Description
employee_idPK	INT	Unique employee identifier
employee_name	VARCHAR(100)	Employee display name
manager_id	INT	Identifier of the employee's manager

tree_a_nodes

Column	Type	Description
node_idPK	INT	Node identifier within tree A
parent_id	INT	Parent node identifier, null for the root
side	VARCHAR(5)	Whether the node is the left or right child
node_value	INT	Value stored in the node

tree_b_nodes

Column	Type	Description
node_idPK	INT	Node identifier within tree B
parent_id	INT	Parent node identifier, null for the root
side	VARCHAR(5)	Whether the node is the left or right child
node_value	INT	Value stored in the node

Your question is SQL Self Join and Tree Checks. Start with the requirements and the three tables in the Question tab.

Run and submit as often as you like. When you're ready, talk me through your approach or go straight to the code.