remove and create column otg_id

Author: IlkaCu

dataprocessing/sql_snippets/ego_dp_powerflow_assignment_otgid.sql

@@ -11,8 +11,11 @@ __author__ 	= "IlkaCu"
 */
 
 -- Set column otg_id to NULL 
-UPDATE model_draft.ego_dp_supply_res_powerplant
-	SET otg_id = NULL; 
+ALTER TABLE model_draft.ego_dp_supply_res_powerplant
+	DROP COLUMN otg_id; 
+	
+ALTER TABLE model_draft.ego_dp_supply_res_powerplant
+	ADD COLUMN otg_id; 
 
 -- Insert otg_id of bus for res pp 
 UPDATE model_draft.ego_dp_supply_res_powerplant a
@@ -27,8 +30,11 @@ UPDATE model_draft.ego_dp_supply_res_powerplant a
 
 
 -- Set column otg_id to NULL 
-UPDATE model_draft.ego_dp_supply_conv_powerplant
-	SET otg_id = NULL; 
+ALTER TABLE model_draft.ego_dp_supply_conv_powerplant
+	DROP COLUMN otg_id; 
+	
+ALTER TABLE model_draft.ego_dp_supply_conv_powerplant
+	ADD COLUMN otg_id;
 
 -- Insert otg_id of bus for conv pp
 UPDATE model_draft.ego_dp_supply_conv_powerplant a