Let there be table A(text_1 varchar2(4000 CHAR), text_2 varchar(4000 CHAR))
And here is the select for this:
SELECT sys.dbms_crypto.hash(empty_clob() || text_1 || text_2, 2) from A;
I am getting error 24805. I am expecting casting text_1 and text_2 to CLOB , and connecting to each other. After that I need to get hash_code using function below. This code will also be part of PL/SQL block ( part of insert statement in function).
If I will use this:
SELECT sys.dbms_crypto.hash(to_clob('') || text_1 || text_2, 2) from A;
Everything is ok now. So, what was the problem?
create table A(text_1 varchar2(4000 CHAR), text_2 varchar2(4000 CHAR));
insert into A(text_1,text_2)values ('test1','test2');
commit;
Here is an example of creating data for A.
You can use TO_CLOB for concatenate your char based columns. Then use CONCAT which seems can work with CLOB. Try below.
SELECT DBMS_CRYPTO.HASH(CONCAT(TO_CLOB (TEXT_1) , TO_CLOB (TEXT_2)), 2) FROM A;