SQL Snippets ™: Tutorials for Oracle Developers

create table t1
( 
  key number, 
  group_key varchar2(10), 
  val varchar2(10)
);

insert into t1 values ( 1, 'Group-1', null );
insert into t1 values ( 2, 'Group-1', null );
insert into t1 values ( 3, 'Group-2', 'a'  );
insert into t1 values ( 4, 'Group-2', 'a'  );
insert into t1 values ( 5, 'Group-2', 'z'  );
insert into t1 values ( 6, 'Group-2', 'z'  );
insert into t1 values ( 7, 'Group-2', null );
insert into t1 values ( 8, 'Group-3', 'A'  );
insert into t1 values ( 9, 'Group-3', 'A'  );
insert into t1 values (10, 'Group-3', 'Z'  );

commit;

set null '(null)'