How to pass dynamicaly values :new.COLUMN_NAME from TRIGGER?

Question

Hello folks,
I have 1 configuration table, which stores information about other table's columns in case when special validation to that column should be performed by validation process.
Then I need to create a before insert, update trigger for validated table (which record exists in above mentioned table) which calls validation process. Into validation process must be passes newly inserted VALUE from column, which is defined in configuration table. How to do this?
Here is settings, which explains more in detail what I'm trying to do:
1. Configuration table:
create table validation_tables
  OBJECT_ID                NUMBER        NOT NULL,
  TIMESTAMP                DATE          DEFAULT CURRENT_TIMESTAMP NOT NULL,
  TABLE_TO_VALIDATE        VARCHAR2(30)  NOT NULL,  -- name of table whoch should be validated
  COLUMN_TO_VALIDATE       VARCHAR2(30)  NOT NULL,  -- column from validated table
  COLUMN_LINKED            VARCHAR2(30)  not null,   
  TABLE_DESCRIPTION        VARCHAR2(300)
);2. Insert 1 record into above table:
insert into validation_tables
values (next_object_id, current_timestamp, 'TK_TEST_OBJECT_NOTE','NOTE','OBJECT_NOTE_TYPE', 'Testing Note Type table - 1st field');
commit;3. create TK_TEST_OBJECT_NOTE table
create table TK_TEST_OBJECT_NOTE
  OBJECT_ID         NUMBER        NOT NULL,
  TIMESTAMP         DATE          DEFAULT CURRENT_TIMESTAMP NOT NULL,
  OBJECT_NOTE_TYPE  number not null,
  NOTE              varchar2(500),
  NOTE2             varchar2(500)
);4. package which will perform some validation (at this stage only validation function calling is important)
create or replace package api_validate is
   function validate_field (pv_value_to_validate varchar2, pv_linked_object_number number) return varchar2;
end api_validate;
create or replace package body api_validate is
  function validate_field (pv_value_to_validate varchar2, pv_linked_object_number number) return varchar2
  is
  begin
    dbms_output.put_line('pv_value_to_validate    :'||pv_value_to_validate);
    dbms_output.put_line('pv_linked_object_number :'||pv_linked_object_number);
    return '-1';
  end;
end api_validate;5. before insert update trigger for TK_TEST_OBJECT_NOTE => this must be modified
create or replace trigger VAL#BI#TK_TEST_OBJECT_NOTE
before insert or update on TK_TEST_OBJECT_NOTE
for each row
declare
  cursor c is
    select column_to_validate, column_linked
      from validation_tables
      where TABLE_TO_VALIDATE = 'TK_TEST_OBJECT_NOTE';
  l_valid varchar2(250);
  l_value_to_validate varchar2(4000);
  l_validated_obj_number number;
  cmd varchar2(250); -- command
begin
  for x in c loop
    dbms_output.put_line('x.column_to_validate:'||x.column_to_validate||' x.column_linked:'||x.column_linked);
    cmd := 'begin
               l_value_to_validate := :new.'||x.column_to_validate||';               -- << need to assign value based on configuration table ("validation_tables")
               l_validated_obj_number := :new.'||x.column_linked||';
            end;';
    dbms_output.put_line(cmd);
    EXECUTE IMMEDIATE cmd;
    --l_value_to_validate := :new.NOTE;                                     -- if configuration "validation_tables" table wouldn't be in use, then I would use easily this
    --l_validated_obj_number := :new.OBJECT_NOTE_TYPE;
    dbms_output.put_line('l_value_to_validate:'||l_value_to_validate);
    dbms_output.put_line('column_linked VALUE:'||l_validated_obj_number);
    l_valid := api_validate.validate_field(l_value_to_validate, l_validated_obj_number);
    --l_valid := '-1';
    if l_valid <> '-1' then
       raise_application_error(-20001, l_valid);
    end if;
  end loop;
end;
/6. Try to insert into TK_TEST_OBJECT_NOTE
insert into TK_TEST_OBJECT_NOTE
values (next_object_id, current_timestamp, 54321,'Some TEST text for Note 1','Note 2 text');7. Expected output for step 6:
in dbms_output:
x.column_to_validate:NOTE x.column_linked:OBJECT_NOTE_TYPE
pv_value_to_validate    :Some TEST text for Note 1
pv_linked_object_number :54321
and then:
update validation_tables vt
  set vt.column_to_validate = 'NOTE2'
where vt.table_to_validate = 'TK_TEST_OBJECT_NOTE';
again the same insert from 6:
insert into TK_TEST_OBJECT_NOTE
values (next_object_id, current_timestamp, 54321,'Some TEST text for Note 1','Note 2 text');
expected output:
x.column_to_validate:NOTE2 x.column_linked:OBJECT_NOTE_TYPE
pv_value_to_validate    :Note 2 text
pv_linked_object_number :54321So my problem is with trigger in above section 5. I need to pass VALUE into called "api_validate.validate_field" function based on settings in configuration "validation_tables" table.
Any idea?
Thanks,
Tomas

Answer 1

hmm it seems like the only option would be hardcodeing it for every column in table - what I really don't like very much :-(
create or replace trigger VAL#BI#TK_TEST_OBJECT_NOTE
before insert or update on TK_TEST_OBJECT_NOTE
for each row
declare
  cursor c is
    select column_to_validate, column_linked
      from validation_tables
      where TABLE_TO_VALIDATE = 'TK_TEST_OBJECT_NOTE';
  l_valid varchar2(250);
  l_value_to_validate varchar2(4000);
  l_validated_obj_number number;
  cmd varchar2(250); -- command
begin
  for x in c loop
    dbms_output.put_line('x.column_to_validate:'||x.column_to_validate||' x.column_linked:'||x.column_linked);
    if x.column_to_validate = 'NOTE' then
       l_value_to_validate := :new.NOTE;
    elsif x.column_to_validate = 'NOTE2' then
       l_value_to_validate := :new.NOTE2;
    end if;  
    if x.column_linked = 'NOTE' then
       l_validated_obj_number := :new.NOTE;
    elsif x.column_linked = 'NOTE2' then
       l_validated_obj_number := :new.NOTE2;
    elsif x.column_linked = 'OBJECT_NOTE_TYPE' then
       l_validated_obj_number := :new.OBJECT_NOTE_TYPE;      
    end if;
    l_valid := api_validate.validate_field(l_value_to_validate, l_validated_obj_number);
    --l_valid := '-1';
    if l_valid <> '-1' then
       raise_application_error(-20001, l_valid);
    end if;
  end loop;
end;
/