Ask about UTL_FILE in Stored Procedure

Question

Hi
I was trying to do an insert in a table which then trigger a stored procedure to write the inserted data to a text file. However, I have some issues here in the Stored Procedure. Thanks for trying to help... [Insert -> Table -> Trigger -> Stored Procedure -> Text File]
----User will execute this sql
----insert into tester.test_table values ('ab');
CREATE TABLE TESTER.TEST_TABLE
  LINECODE  VARCHAR2(2 BYTE)
----Just for testing purpose
CREATE TABLE TESTER.TEST_REC_TABLE
  LINECODE  VARCHAR2(2 BYTE)
CREATE OR REPLACE TRIGGER TESTER.TRIGGER_AUDIT
AFTER INSERT OR UPDATE
ON TESTER.TEST_TABLE REFERENCING OLD AS OLD NEW AS NEW
FOR EACH ROW
DECLARE
  sLineCode VARCHAR2(2);
BEGIN
   sLineCode := '';
    IF UPDATING THEN     
      sLineCode := :NEW.LINECODE;
      TRIGGER_PACKAGE.WRITE_FILE(sLineCode);
    END IF;  
    IF INSERTING THEN
      sLineCode := :NEW.LineCode;
      TRIGGER_PACKAGE.WRITE_FILE(sLineCode);
    END IF;
EXCEPTION
    WHEN others then null;
END TRIGGER_AUDIT;
CREATE OR REPLACE PACKAGE BODY TESTER.TRIGGER_PACKAGE
is
   procedure WRITE_FILE(in_LineCode in varchar2)
   is
     sLineCode varchar2(2);  
     v_FileHandle UTL_FILE.FILE_TYPE;
----some checking of the input data for NULL 
   begin  
    if ((rtrim(in_LineCode) IS NULL) or (in_LineCode is null)) then
        sLineCode := 'XX';
    else
        sLineCode := in_LineCode;          -------->PROBLEM HERE?
    end if;
    if (length(sLineCode) > 2) then
      sLineCode := substr(sLineCode,1,2);
    end if;
    Insert into TEST_REC_TABLE (LineCode) values (sLineCode); ----insert data to another table for testing
    EXECUTE IMMEDIATE 'CREATE OR REPLACE DIRECTORY FILEDIR AS ' || '''' || 'c:\' || '''';
    v_FileHandle := UTL_FILE.FOPEN('FILEDIR','Test_Table.txt','w'); ----write to text file in C:\Test_Table.txt
    UTL_FILE.PUT_LINE(v_FileHandle, 'Inserted ' || sLineCode || ' @ ' || TO_CHAR(SYSDATE,'DD-MM-YYYY HH:MI:SS AM'));
    UTL_FILE.FCLOSE(v_FileHandle);           
   exception
      when others then null;
   end;
end TRIGGER_PACKAGE;
1) The problem I faced is that when I perform INSERT sql for the new data, it can be successfully be inserted into both tables TEST_REC_TABLE and TEST_TABLE, but it just does not write to the text file.
2) However, when I just execute the procedure I will get XX for the input data as it is NULL. This XX data will then be seen in TEST_REC_TABLE as "XX" record and Test_Table.txt as "Inserted XX @ 10-01-2014 04:56:06 PM". UTL_FILE did write to textfile so my guess is that it could be due to my poor understanding of logic in the checking of the input data for NULL. Tried but I am still clueless, thanks for pointing out the issue.

Answer 1

> 1) I'm just testing and learning here with trigger insert...
Good. In that case its just a wrong choice that you have decided to write to a file from trigger. Oracle base is a good site. They have examples too. Please check that ORACLE-BASE - Database Triggers Overview.
> 2) How should I do then?
Just create the object one time
CREATE OR REPLACE DIRECTORY FILEDIR AS <path>
The path should be a location in your server where oracle is installed.
> 3) How should I do then? Use this ?
EXCEPTION
      WHEN OTHERS THEN
           DBMS_OUTPUT.PUT_LINE
                ('ERROR ' || TO_CHAR(SQLCODE) || SQLERRM);
           NULL;
Don't do any thing. Just remove the exception handling. Don't handle unknown exceptions. If at all you want to handle them for logging purpose RAISE it at the end like this.
exception
  when others then
    <log your messages>
    raise;
And about exception handling one of the forum member BluShadow has written a nice article PL/SQL 101 : Exception Handling. That would be a nice read.