Illegal use of LONG datatype Oracle

this is my firt question here

I have a problem trying to convert a table column (long raw) to a base 64 string, this column contains some of the employees pictures.

This is the query, the field that i'm trying to convert is f.fot_empl:

SELECT e.NOM_EMPL First_name,
       APE_EMPL Last_name,
       e.NOM_EMPL || ' ' || e.APE_EMPL Full_name,
       car.NOM_CARG position,
       COS.NOM_CCOS Area,
       f.fot_empl Picture, 
       E.FEC_NACI Birth_date
  FROM EMPLE e
       INNER JOIN CONTR c
          ON E.COD_EMPL = C.COD_EMPL
       INNER JOIN cargo car
          ON C.COD_CARG = CAR.COD_CARG
       INNER JOIN CCOST cos
        on COS.COD_CCOS = C.COD_CCOS
       LEFT JOIN FOEMP f -- employee picture
          ON e.cod_empl = F.COD_EMPL
 WHERE C.IND_ACTI = 'A';

What i have tried:

The accepted answer of this post with no results, i keep getting "Illegal use of LONG datatype" error. Workaround for ORA-00997: illegal use of LONG datatype

I try to implement the following function with no results:

CREATE OR REPLACE FUNCTION to_base64 (
       vcodem     IN FOEMP.COD_EMPR%TYPE,
       vcodempl   IN FOEMP.COD_EMPL%TYPE)
       RETURN VARCHAR2
    IS
       V_VAR      FOEMP.FOT_EMPL%TYPE;
       V_result   VARCHAR2 (4000);
    BEGIN
       DBMS_OUTPUT.put_line ('Start');
       SELECT UTL_RAW.cast_to_varchar2 (
                 UTL_ENCODE.base64_encode (
                    UTL_RAW.cast_to_raw (DBMS_LOB.SUBSTR (f.FOT_EMPL, 4000))))
         INTO V_result
         FROM FOEMP f
        WHERE COD_EMPL = vcodempl AND COD_EMPR = vcodem;
       DBMS_OUTPUT.put_line ('End');
       DBMS_OUTPUT.put_line ('Result: ' || V_result);
    END to_base64;
    /

The function is invalid due to ORA-00997 in:

   SELECT UTL_RAW.cast_to_varchar2 (
             UTL_ENCODE.base64_encode (
                UTL_RAW.cast_to_raw (DBMS_LOB.SUBSTR (f.FOT_EMPL, 4000))))
     INTO V_result
     FROM FOEMP f
    WHERE COD_EMPL = vcodempl AND COD_EMPR = vcodem;

Many thanks in advance.

Solution

1. given the many problems i had with long raw i decide to create a table like this:

   CREATE TABLE FOTS_EMPL ( cod_empr, cod_empl, foto) AS SELECT F.COD_EMPR, F.COD_EMPL, TO_LOB (FOT_EMPL) FROM FOEMP f;

2. i took the function given by @tbone and i added and if condition like this:

   CREATE OR REPLACE FUNCTION base64enc (p_blob IN BLOB) RETURN CLOB AS l_clob CLOB; l_step PLS_INTEGER := 1998; BEGIN IF p_blob IS NOT NULL THEN FOR i IN 0 .. TRUNC ( (DBMS_LOB.getlength (p_blob) - 1) / l_step) LOOP l_clob := l_clob || UTL_RAW.cast_to_varchar2 ( UTL_ENCODE.base64_encode ( DBMS_LOB.SUBSTR (p_blob, l_step, i * l_step + 1))); END LOOP; RETURN l_clob; ELSE RETURN NULL; END IF; END base64enc;

3. this was my final select statement:

   SELECT e.NOM_EMPL First_name, APE_EMPL Last_name, e.NOM_EMPL || ' ' || e.APE_EMPL Full_name, car.NOM_CARG position, COS.NOM_CCOS Area, base64enc(foto) Picture, E.FEC_NACI Birth_date FROM EMPLE e INNER JOIN CONTR c ON E.COD_EMPL = C.COD_EMPL INNER JOIN cargo car ON C.COD_CARG = CAR.COD_CARG INNER JOIN CCOST cos on COS.COD_CCOS = C.COD_CCOS LEFT JOIN FOTS_EMPL F -- new table with blob instead of long raw ON e.cod_empl = F.COD_EMPL AND e.cod_empr = f.cod_empr WHERE C.IND_ACTI = 'A';

Thank you very much.