Oracle generating hash_val from a clob

I have the following table, where I would like the value of hash_val to be generated from clob_val whether clob_val is inserted or updated. Can this be done perhaps by making the column hash_val a virtual column? Or does this have to be done via a function and trigger. I want to use something like the CRYPTO call below to generate the value for hash_val. In addition, I would like hash_val to be the primary KEY Any examples setting up the virtual column if possible would be greatly appreciated. Thanks to all who answer. ~~~ CREATE table table_z( seq_num integer GENERATED BY DEFAULT AS IDENTITY (START WITH 1) NOT NULL, val NUMBER, hash_val VARCHAR2(1000), clob_val CLOB); DBMS_CRYPTO.HASH (clob_val, 6 /*DBMS_CRYPTO.HASH_SH512*/ ) ~~~