Select Non-repeating Planet/Satellite Combinations

devstronomy_random_planet_random_satellite_non_repeat.sql

create table devstronomy.temp_l_satellite like devstronomy.l_satellite;
alter table devstronomy.temp_l_satellite add primary key (id);
alter table devstronomy.temp_l_satellite add column ins_ts timestamp default current_timestamp not null;

insert ignore into devstronomy.temp_l_satellite
select ls.*, current_timestamp
  from devstronomy.l_satellite ls
 where planet_id = (select lp.id 
                      from devstronomy.l_planet lp
                     order by rand() 
                    limit 1) 
   and not exists (select 1 
                     from devstronomy.temp_l_satellite tls
                    where tls.id = ls.id
                    limit 1
                   )
 order by rand() 
 limit 1;
 
select * 
  from devstronomy.temp_l_satellite 
 order by ins_ts desc 
 limit 1;