SQL & PL/SQL

How can I select, in a ora_hash function, all the columns of my table to get a hash value? I have the following query:

select sum(ora_hash(column_1||'|'||column_2||'|'||column_3)) FROM my_table; 

This query gives me a number, it's 13913007220. Now I want to do the same query without having to specifie the names of each column. Something like:

  select sum(ora_hash(*)) FROM my_table; 

(this gives me an error like: 00936. 00000 - "missing expression")

How can I do this?

Thanks in advance.