REGEXP_SUBSTR(строка, '[^;]+', 1, номер элемента)

SELECT REGEXP_SUBSTR('A1;A2;;A4', '[^;]+', 1, 3) FROM DUAL;
F
--
A4

SELECT REGEXP_SUBSTR('A1;A2;;A4', '[^;]*', 1, 3) AS F FROM DUAL;
F
--
A2

DECLARE
   v_file          UTL_FILE.FILE_TYPE;
   v_file_rec      VARCHAR2(32000);
   v_sep_symb      CONSTANT CHAR(1 CHAR) := ';';
BEGIN
   ...
   v_file := UTL_FILE.FOPEN(
      location     => ..., 
      filename    => ..., 
      open_mode   => 'r'
   );
   ...
   UTL_FILE.GET_LINE(FILE => v_file, BUFFER => v_file_rec);
   ...
   INSERT INTO TBL_FILE
   SELECT
      ...
      REGEXP_SUBSTR(v_file_rec, '[^' || v_sep_symb || ']+', 1,   1)    AS C001,
      ...
      REGEXP_SUBSTR(v_file_rec, '[^' || v_sep_symb || ']+', 1, 100)    AS C100                                        
   FROM DUAL;
   ...
   COMMIT;
END;

SELECT 
    LEVEL AS NUM, 
    REGEXP_SUBSTR(';;A3;;;A6;;', '([^;]+|)(;?)', 1, LEVEL, NULL, 1) AS ITEM 
FROM DUAL
CONNECT BY LEVEL <= REGEXP_COUNT(';;A3;;;A6;;', ';') +1;

NUM ITEM
--- ----
1	
2	
3   A3
4	
5	
6   A6
7	
8