error on self join

I need to run the following query: SELECT WRK_ImplDisp_1.Livello, WRK_ImplDisp_1.Origine, WRK_ImplDisp.Padre, WRK_ImplDisp_1.Figlio, WRK_ImplDisp.QUnit*WRK_ImplDisp_1.QUnit AS Espr1, WRK_ImplDisp_1.DaAggregare, -1 AS Espr2 FROM WRK_ImplDisp INNER JOIN WRK_ImplDisp AS WRK_ImplDisp_1 ON WRK_I

error on self join

I need to run the following query: SELECT WRK_ImplDisp_1.Livello, WRK_ImplDisp_1.Origine, WRK_ImplDisp.Padre, WRK_ImplDisp_1.Figlio, WRK_ImplDisp.QUnit*WRK_ImplDisp_1.QUnit AS Espr1, WRK_ImplDisp_1.DaAggregare, -1 AS Espr2 FROM WRK_ImplDisp INNER JOIN WRK_ImplDisp AS WRK_ImplDisp_1 ON WRK_ImplDi