Мы можем попробовать использовать REGEXP_SUBSTR
:
WITH yourTable AS (
SELECT 'amount = 7995 ;channel = SXXXN21 ;group_header = NPS099 ;currency = EUR' AS col FROM dual
)
SELECT
REGEXP_SUBSTR(col, '(^|\s|;)group_header = (.*?)\s*(;|$)', 1,1,NULL,2)
FROM yourTable;