Exam 70-761 topic 1 question 12 discussion

DRAG DROP -
Note: This question is part of a series of questions that use the same scenario. For your convenience, the scenario is repeated in each question. Each question presents a different goal and answer choices, but the text of the scenario is exactly the same in each question in this series.
You query a database that includes two tables: Project and Task. The Project table includes the following columns:


Task level is defined using the following rules:

You need to determine the task level for each task in the hierarchy.
Which five Transact-SQL segments should you use to develop the solution? To answer, move the appropriate Transact-SQL segments from the list of Transact-
SQL segments to the answer area and arrange them in the correct order.
Select and Place:

Suggested Answer:
Box 1: SELECT CAST (NULL AS INT) AS ParentTaskID, etc.
This statement selects all tasks with task level 0.
The ParentTaskID could be null so we should use CAST (NULL AS INT) AS ParentTaskID.

Box 2: UNION -
We should use UNION and not UNION ALL as we do not went duplicate rows.
UNION specifies that multiple result sets are to be combined and returned as a single result set.
Incorrect Answers:
Not UNION ALL: ALL incorporates all rows into the results. This includes duplicates. If not specified, duplicate rows are removed.
Box 3, Box 4, Box 5:
These statements select all tasks with task level >0.
References:
https://msdn.microsoft.com/en-us/library/ms180026.aspx