title: The maximum recursion 100 has been exhausted before statement completion
body: <p>I keep getting a <strong><code>max recursion error</code></strong> with this query.</p>
  
  <p>At first I thought it was because a null was being returned and then it would try and match the null values causing the error however, I rewrote my query so nulls aren't returned and the error still occurs.</p>
  
  <p>What would be the best way to rewrite this function, so that the error will not occur</p>
  
  <pre><code>WITH EmployeeTree AS
  (
      SELECT 
          EMP_SRC_ID_NR Id, USR_ACV_DIR_ID_TE Uuid, 
          CASE Employees.APV_MGR_EMP_ID 
             WHEN Null THEN '0' 
             ELSE Employees.APV_MGR_EMP_ID 
          END as  ApprovalManagerId 
      FROM 
          dbo.[tEmployees] as Employees WITH (NOLOCK)
      WHERE 
          APV_MGR_EMP_ID = @Id 
          and Employees.APV_MGR_EMP_ID is not null 
          and Employees.EMP_SRC_ID_NR is not null  
  
      UNION ALL
  
      SELECT 
          EMP_SRC_ID_NR Id, USR_ACV_DIR_ID_TE Uuid, 
          CASE Employees.UPS_ACP_EMP_NR 
             WHEN Null THEN '1' 
             ELSE Employees.UPS_ACP_EMP_NR 
          END as ApprovalManagerId 
      FROM 
          dbo.[tEmployees] as Employees WITH (NOLOCK)
      WHERE 
          UPS_ACP_EMP_NR = @Id 
          and Employees.APV_MGR_EMP_ID is not null 
          and Employees.EMP_SRC_ID_NR is not null  
  
      UNION ALL
  
      SELECT 
          Employees.EMP_SRC_ID_NR, Employees.USR_ACV_DIR_ID_TE, 
          CASE Employees.APV_MGR_EMP_ID 
              WHEN Null THEN '2' 
              ELSE Employees.APV_MGR_EMP_ID 
          END  
      FROM 
          dbo.[tEmployees] as Employees WITH (NOLOCK)
      JOIN 
          EmployeeTree ON Employees.APV_MGR_EMP_ID = EmployeeTree.Id 
      where  
          Employees.APV_MGR_EMP_ID is not null 
          and Employees.EMP_SRC_ID_NR is not null             
  )
  SELECT 
      Id AS [EmployeeId], 
      Uuid AS [EmployeeUuid], 
      ApprovalManagerId AS [ManagerId] 
  FROM EmployeeTree        
  </code></pre>