Hi!
First i want to thank you for the many Responses that where usefull for me.

Í need a constraint or trigger that controls if the row inserted or updated contains a range of numbers that is already contained in another row of the same table.

Example:
Create table test as select 1 as id, 10 as n_from, 20 as n_to from dual;

Table test has now a record with numbers from 10 (n_from) to 20 (n_to).

How can I prevent an insert of a row like this (id, n_from, n_to)
2,11,12
Or
2,13,20

Both ranges are contained into the range 10-20.
Í need to raise an error when an existing range contains the new/updated range.

Í know how to do this with procedures but i need doing this in a constraint (cannot use querys) or trigger (mutating) to avoid the problem even in manualy inserted/updated rows.

Sorry for my english.