What are the key requirements to write a recursive cte?

Question

what are the key requirements to write a recursive cte?
when we will go for a recursive cte.

Answer 1

A common table expression (CTE) can be thought of as a temporary result set that is defined within the execution scope of a single SELECT, INSERT, UPDATE, DELETE, or CREATE VIEW statement. A CTE is similar to a derived table in that it is not stored as an
object and lasts only for the duration of the query. Unlike a derived table, a CTE can be self-referencing and can be referenced multiple times in the same query.
A CTE can be used to:
Create a recursive query. For more information, see https://technet.microsoft.com/en-us/library/ms186243%28v=sql.105%29.aspx
Substitute for a view when the general use of a view is not required; that is, you do not have to store the definition in metadata.
Enable grouping by a column that is derived from a scalar subselect, or a function that is either not deterministic or has external access.
Reference the resulting table multiple times in the same statement.
Source : https://technet.microsoft.com/en-us/library/ms190766%28v=sql.105%29.aspx