Du kan använda CTE enligt följande.
with pfcc as
(select REGEXP_SUBSTR(delimited , '[^\]+', 1, 1) colA,
REGEXP_SUBSTR(delimited , '[^\]+', 1, 2) colB,
REGEXP_SUBSTR(delimited , '[^\]+', 1, 3) colC,
REGEXP_SUBSTR(delimited , '[^\]+', 1, 4) colD
from products
where productid = 1)
select * from pfcc tmp
inner join lineitems gch
on gch.Line = tmp.colA
AND gch.productB = tmp.colB
AND gch.productC = tmp.colC;