create table deathstar_protocols ( 
  id integer not null primary key, 
  label varchar2(256), 
  alert_level varchar2(16) not null, 
  defense_mode varchar2(32) not null, 
  power_level number(5,2) not null 
)

insert into deathstar_protocols 
  values (1, 'Everything easy', 'LOW', 'BE_KIND', 80)

insert into deathstar_protocols 
  values (2, 'Be careful', 'MEDIUM', 'BE_SUSPICIOUS', 90)

insert into deathstar_protocols 
  values (3, 'OMG the rebels!', 'VERY HIGH', 'SHOOT_FIRST_ASK_LATER', 120)

select * from deathstar_protocols

create table deathstar_protocol_active ( 
  id integer not null primary key, 
  only_one number(1) default 1 not null, 
  -- ID is also foreign key 
  constraint deathstar_prot_act_fk 
    foreign key ( id ) 
    references deathstar_protocols ( id ) 
    on delete cascade, 
  -- Make sure there can only be one row 
  constraint deathstar_prot_act_uq 
    unique ( only_one ), 
  -- by limiting the possible value of the 
  -- helper-column 
  constraint deathstar_prot_act_chk 
    check ( only_one = 1 ) 
)

insert into deathstar_protocol_active ( id ) values (1 )

insert into deathstar_protocol_active ( id ) values ( 2 )

create or replace view v_deathstar_protocols 
  as 
  select 
    prot.id, label, alert_level, defense_mode, power_level, 
    coalesce(active.only_one, 0) is_active 
  from 
    deathstar_protocols prot 
    left outer join deathstar_protocol_active active 
      on prot.id = active.id 

select * from v_deathstar_protocols

update deathstar_protocol_active set id = 2

select * from v_deathstar_protocols