How to get result from parent child table

Question

Work on SQL-Server. My table structure is below

CREATE TABLE [dbo].[AgentInfo](
    [AgentID] [int] NOT NULL,
    [ParentID] [int] NULL,
 CONST         


        

Answer 1

You can try this, to get a tree of the elements:

WITH CTE_AgentInfo(AgentID, ParentID, BaseAgent)
AS(
  SELECT 
    AgentID,
    ParentID,
    AgentID AS BaseAgent
   FROM AgentInfo
   WHERE ParentID = -1
  UNION ALL
     SELECT 
    a.AgentID,
    a.ParentID,
    a.AgentID AS BaseAgent
   FROM AgentInfo a
   INNER JOIN CTE_AgentInfo c ON
    c.AgentID = a.ParentID
  )
SELECT * FROM CTE_AgentInfo

And here is an SQLFiddle demo to see it.