select
name,
md5(indvl_id_nbr) as indvl_id_nbr,
case when char_length(indvl_id_nbr)=18 or char_length(indvl_id_nbr)=15 then substring(indvl_id_nbr from 1 for 6)
end as id_prefix, 
case when char_length(indvl_id_nbr)=18 then substring(indvl_id_nbr from 7 for 8) 
when char_length(indvl_id_nbr)=15 then  '19' || substring(indvl_id_nbr from 7 for 6) 
else null end as id_brth_dt
from myschema.table_test;