create table  EduEst.dbo.Group_Node
   (
	Id int not null  primary key  Identity
   )



create table  EduEst.dbo.Group_Child
   (
	Source int not null FOREIGN KEY  REFERENCES  EduEst.dbo.Group_Node(ID) ON DELETE CASCADE,
	Destination int not null FOREIGN KEY  REFERENCES  EduEst.dbo.Group_Node(ID) ON DELETE CASCADE,
	primary key(Source,Destination),	
   )



 

create table Group_Node
(
 Id number not null primary key
);



create table Group_Child 
(	
 Source number not null,
 Destination number not null,
 primary key(Source,Destination),
 FOREIGN KEY(Source) REFERENCES Group_Node ON DELETE CASCADE
 );