Outer join 3 ou mais tabelas no Laravel 8

select ts recordtime, max(to1) tempout, max(to2) tempoutstamb, max(to3) tempoutstamb2
from (
  select ts, tempout to1, cast (null as numeric(10,1)) to2, cast (null as numeric(10,1)) to3
  from table1
union all 
  select ts, null, tempout, null
  from table2
union all
  select ts, null, null, tempout
  from table3
) tt
group by ts
order by ts;