I have created an involved CTE, with no recursion, but with multiple selects being done as it processes the business logic of the requirement. Though, I have been advised that the logic needed for the scenario where no rows are returned, should instead to return all rows found from one of the middle CTEs select instead of the final operation.
How can this be achieved?
Note the following example is basic interpretation of my process and the operation in question occurs after multiple cascaded CTE selects are done an essentially chained together.
Example (as found on SQLFiddle)
In a User Table there are two records where the ids of UserIds are 1 and 2. The first CTEs select, TargetUsers will return no rows requiring the the third CTE, ComputeWithUsers, to use the AllUsers instead.
WITH TargetUsers AS( SELECT * FROM Users WHERE UserId > 5), AllUsers AS( SELECT * FROM Users), ComputeWithUsers(-- This CTE will determine it needs to use `AllUsers` and not `TargetUsers`)Or is there a way to make the TargetUsers select smart enough to extract all users when its main operation returns no rows?