垂直合体を作成するためにグループ化する

それがまさにpivot 対象：

select 
  transaction, 
  "'BBK'",
  "'SBK'",
  "'OBK'",
  "'IBK'"
from (
  select 
  regexp_substr("col_a", '[^~]+', 1, 1) as transaction,
  regexp_substr("col_a", '[^~]+', 1, 2) as code,
  regexp_substr("col_a", '[^~]+', 1, 3) as country
  from Table1 t)
pivot 
( 
  MAX(country) for code in ('BBK','SBK','OBK','IBK')
);