Read Fixed length file

Question

I have a text file that has data in specific positions of the file.
ie.
Pos 1-20 Name
Pos 21-30 Division
Pos 31-38 Birthdate
I saved the file in the DB and want to process it to read the data in the specific positions I listed above.
I started with the code below, but not sure how to get to the specific positions in the file.
DECLARE
v_blob_data BLOB;
v_blob_len NUMBER;
v_clob_data CLOB := 'anything';
v_clob_len NUMBER;
dest_offset NUMBER := 1;
src_offset NUMBER := 1;
blob_csid NUMBER := dbms_lob.default_csid;
lang_ctx INTEGER := dbms_lob.default_lang_ctx;
warning INTEGER;
BEGIN
select blob_content into v_blob_data from wwv_flow_files;
v_blob_len := dbms_lob.getlength(v_blob_data);
dbms_lob.converttoclob(v_clob_data, v_blob_data, v_blob_len,dest_offset,src_offset,blob_csid,lang_ctx,warning);
END;

Answer 1

bobmagan wrote:
Unfortunately, I have to do this inside of an APEX page using pl/sql.What is unfortunate about that!? Apex is good. PL/SQL is awesome.{noformat} :-) {noformat}
I would not have it any other way. Seriously.
If the file is uploaded into Apex - then you still can use external tables.
The basic steps are:
1. spool the uploaded file (from the Apex flow files table) to the local file system of the Oracle server using UTL_FILE
2. alter the external table and specify the newly created file's location
3. select from the external data to load the file contents
Alternatively, you need to write your own CLOB parser - that can read lines from the CLOB, parse these, and output the tokens to use (e.g. token 1 is the invoice id, token 2 the invoice date, etc).
This all is very much doable in PL/SQL. And Apex is PL/SQL - and allows you to call your own PL/SQL packages and code to process data.
Keep in mind that the simpler a process is, the easier it is to write, maintain and debug. Doing manual parsing.. not something that should be treated lightly as that can become quite complex.
Dealing with an external table and its easy definition of the format of the file content to load, is a lot easier and more flexible. The only downside is having to spool the CLOB to an external file in order to use the external table... However... I do recall a few months ago looking at the "cartridge" used by Oracle to load external files as an external table, and read/saw something that seemed to also support CLOBs..?
So I'm not sure if one can now define an external table and use it to load CLOB contents - worth looking at... and even if not, also worth considering spooling a CLOB to external file for loading via the external table interface.
Unless of course you're keen to put your regex kung fu skills to use in writing a custom CLOB parser for the file contents.