Question

Inside of a trigger I’m trying to loop over all columns on a table and compare the new values to the old values. Here is what I have so far:

CREATE OR REPLACE TRIGGER 'JOSH'.TEST#UPD BEFORE  UPDATE ON 'JOSH'.'TEST_TRIGGER_TABLE' REFERENCING OLD AS OLD NEW AS NEW FOR EACH ROW declare        oldval varchar(2000);       newval varchar(2000);    begin        for row in (SELECT column_name from user_tab_columns where table_name='TEST_TRIGGER_TABLE') loop        execute immediate 'select :old.'||row.column_name||' from dual'   into oldval;        execute immediate 'select :new.'||row.column_name||' from dual'   into newval;        --Do something here with the old and new values    end loop;   end; 

The trigger compiles, but when the trigger fires, I’m getting:

ORA-01008: not all variables bound

on the first execute immediate because it’s expecting a value for :old. :old and :new are already defined as part of the trigger, but it appears that execute immediate can’t see those variables.

Is there a way to dynamically iterate over the column values in a trigger?

Answer 1

No, you cannot reference :old and :new values dynamically. As Shane suggests, you can write code to generate the static trigger code, if that makes life easier. Also, you can make ‘do something here’ into a package procedure so that your trigger becomes:

CREATE OR REPLACE TRIGGER JOSH.TEST#UPD BEFORE  UPDATE ON JOSH.TEST_TRIGGER_TABLE begin        my_package.do_something_with (:old.col1, :new.col1);    my_package.do_something_with (:old.col2, :new.col2);    my_package.do_something_with (:old.col3, :new.col3);    -- etc. end; 

(You can ditch the pointless REFERENCING clause by the way).