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Self Join

  
 ---- A table can be joined to itself in a self-join 
      
      

      

      tblWorld
      

      

      CountryID      
      Name    
      ContinentID 
      

      

      1
      Vijay
      3
      

      

      2
      USA
      4
      

      

      3
      Asia
      NULL
      

      

      4
      N.America
      NULL
      

      

      5
      Nepal
      3
      

      

      6
      Canada
      4
      

      


      SELECT      c1.name AS Continent, c2.Name Country
      FROM        tblWorld c1
      JOIN        tblWorld c2
      ON          c1.CountryID = c2.ContinentID

      

      

      Output
      

      

      Continent 
      Country      
      

      

      Asia
      India
      

      

      Asia
      Nepal
      

      

      N.America
      USA
      

      

      N.America
      Canada