Recursive CTE query in SQL Server - sql

Question

I've looked at many recursive CTE examples on this site already and I've tried applying this to my own data. I seem to have a few more joins than most examples but I think I'm getting there. The problem I want help with is that I get an error saying:
The statement terminated. The maximum recursion 100 has been exhausted before statement completion.
I have run the first select statement of the CTE and I've repeatedly run the second select statement (with different actual position codes) and for this employee there are six levels so I can't see why I get the error.
My one area of suspicion is that I have to apply the criteria 'relationship_type_id = 0' as this is the 'Reports To' relationship type. I had tried making this a left outer join but they aren't allowed. This means I don't get the top level manager using this query (i.e. the person with no manager themselves).
I've posted the code below and any help would be much appreciated.
WITH EmployeeHierarchy (EmployeeID, LastName, FirstName, PositionCode, ReportsTo, HierarchyLevel) AS
(
SELECT
p.employee_id as EmployeeID,
p.last_name as LastName,
p.first_name as FirstName,
pos.position_code as PositionCode,
r.to_position_code as ReportsTo,
1 as HierarchyLevel
FROM
--JOIN: Personal details
dbo.person p
--JOIN: Employment links a person to a post (could have more than one)
INNER JOIN
dbo.employment e ON e.employee_id = p.employee_id
--JOIN: details of the position held
INNER JOIN
dbo.position pos ON pos.position_code = e.position_code
--JOIN: Relationships between the positions, one position reports to another position etc.
-- There are several 'relationship types', we are only interested in relationship_type_id = 0
-- as this is the 'Reports to' relationship code. Others types include 'Managed by' etc.
INNER JOIN
dbo.relationship r ON r.from_position_code = pos.position_code AND r.relationship_type_id = 0
WHERE
--CRITERIA: Use my employee Id as a starting point for testing
p.employee_id = '10076395'
UNION ALL
-- Recursive step
SELECT
p2.employee_id as EmployeeID,
p2.last_name as LastName,
p2.first_name as FirstName,
pos2.position_code as PositionCode,
r2.to_position_code as ReportsTo,
eh.HierarchyLevel + 1 AS HierarchyLevel
FROM
dbo.person p2
INNER JOIN
dbo.employment e2 ON e2.employee_id = p2.employee_id
INNER JOIN
dbo.position pos2 ON pos2.position_code = e2.position_code
INNER JOIN
dbo.relationship r2 ON r2.from_position_code = pos2.position_code AND r2.relationship_type_id = 0
--JOIN: Link this query back to the base query
INNER JOIN
EmployeeHierarchy eh ON r2.from_position_code = eh.PositionCode
)
SELECT *
FROM EmployeeHierarchy
ORDER BY HierarchyLevel, LastName, FirstName

Answer 1

Give this a try.
I've moved the complex joins to a separate CTE to keep the recursive section as clean and as simple as possible. If nothing else this approach should help you pinpoint your issue.
; WITH employees AS (
SELECT person.employee_id
, person.last_name
, person.first_name
, position.position_code
, relationship.to_position_code
FROM dbo.person
INNER
JOIN dbo.employment
ON employment.employee_id = person.employee_id
INNER
JOIN dbo.position
ON position.position_code = employment.position_code
INNER
JOIN dbo.relationship
ON relationship.from_position_code = position.position_code
AND relationship.relationship_type_id = 0
)
, recursive_bit AS (
SELECT employee_id
, last_name
, first_name
, position_code
, to_position_code
FROM employees
WHERE employee_id = '10076395'
UNION ALL
SELECT employees.employee_id
, employees.last_name
, employees.first_name
, employees.position_code
, employees.to_position_code
FROM recursive_bit
INNER
JOIN employees
ON employees.position_code = recursive_bit.to_position_code
)
SELECT *
FROM recursive_bit

Answer 2

Please try :
WITH EmployeeHierarchy (EmployeeID, LastName, FirstName, PositionCode, ReportsTo, HierarchyLevel) AS
(
SELECT
p.employee_id as EmployeeID,
p.last_name as LastName,
p.first_name as FirstName,
pos.position_code as PositionCode,
r.to_position_code as ReportsTo,
1 as HierarchyLevel
FROM
--JOIN: Personal details
dbo.person p
--JOIN: Employment links a person to a post (could have more than one)
INNER JOIN dbo.employment e
ON e.employee_id = p.employee_id
--JOIN: details of the position held
INNER JOIN dbo.position pos
ON pos.position_code = e.position_code
--JOIN: Relationships between the positions, one position reports to another position etc.
-- There are several 'relationship types', we are only interested in relationship_type_id = 0
-- as this is the 'Reports to' relationship code. Others types include 'Managed by' etc.
INNER JOIN dbo.relationship r
ON r.from_position_code = pos.position_code
and r.relationship_type_id = 0
WHERE
--CRITERIA: Use my employee Id as a starting point for testing
p.employee_id = '10076395'
UNION ALL
-- Recursive step
SELECT
p2.employee_id as EmployeeID,
p2.last_name as LastName,
p2.first_name as FirstName,
pos2.position_code as PositionCode,
r2.to_position_code as ReportsTo,
eh.HierarchyLevel + 1 AS HierarchyLevel
FROM
dbo.person p2
INNER JOIN dbo.employment e2
ON e2.employee_id = p2.employee_id
INNER JOIN dbo.position pos2
ON pos2.position_code = e2.position_code
INNER JOIN dbo.relationship r2
ON r2.from_position_code = pos2.position_code
and r2.relationship_type_id = 0
--JOIN: Link this query back to the base query
INNER JOIN EmployeeHierarchy eh
ON r2.from_position_code = eh.ReportsTo
)
SELECT *
FROM EmployeeHierarchy
ORDER BY HierarchyLevel, LastName, FirstName