In the link below I found a brief exchange of ideas between Dr_Gori and Charlesmafra about how Oracle treats null and blank ''.
http://en.glufke.net/oracle/viewtopic.php?p=357
Now tell me: How would I do for Oracle to identify a blank field? (In the case of MSSQL Server, null and '' are two different things).
to which it seems to me when saving a column with a blank value (and no null) Oracle interprets with null.
See the code suggested by CharlesMafra:
DECLARE
A VARCHAR2(10);
BEGIN
--A:='';
IF A is NULL
THEN DBMS_OUTPUT.PUT_LINE('Esse é null!');
END IF;
END;
DECLARE
A VARCHAR2(10);
BEGIN
A:='';
IF A like ''
THEN DBMS_OUTPUT.PUT_LINE('Esse é null!');
END IF;
END;