SELECT
 ASCIISTR(ref_str) ascii_str,
 RAWTOHEX(ref_str) raw_to_hex,
 UTL_RAW.CAST_TO_VARCHAR2(RAWTOHEX(ref_str)) cast_2_varchar2, 
 UTL_RAW.CAST_TO_VARCHAR2(HEXTORAW(RAWTOHEX(ref_str)))  hex_2_raw 
FROM
 (SELECT 'Hello World' ref_str FROM DUAL);

-- Get Monday dates

SELECT
 TO_CHAR(ref_date,'mm/dd/yyyy') ref_date,
 NEXT_DAY(ADD_MONTHS(TRUNC(ref_date,'MON'),-1),'MON') prev_1st_Monday,
 NEXT_DAY(TRUNC(ref_date,'MON'),'MON') curr_1st_Monday,
 DECODE(TO_CHAR(LAST_DAY(TRUNC(ref_date,'MON')),'DY'),
  'MON',LAST_DAY(TRUNC(ref_date,'MON')),
  'TUE',LAST_DAY(TRUNC(ref_date,'MON'))-1,
  'WED',LAST_DAY(TRUNC(ref_date,'MON'))-2,
  'THU',LAST_DAY(TRUNC(ref_date,'MON'))-3,
  'FRI',LAST_DAY(TRUNC(ref_date,'MON'))-4,
  'SAT',LAST_DAY(TRUNC(ref_date,'MON'))-5,
  'SUN',LAST_DAY(TRUNC(ref_date,'MON'))-6
  ) last_monday
FROM 
 (SELECT TO_DATE(&yyyymmdd,'yyyymmdd') ref_date FROM DUAL);

-- Convert to ASCII or EBCDIC

SELECT
 CONVERT(1234567890, 'US7ASCII', 'WE8EBCDIC500') to_ascii,
 CONVERT(1234567890, 'WE8EBCDIC500', 'US7ASCII') to_ebcdic
FROM DUAL
;

-- Convert to UTF8 to WE8EBCDIC500 and reverse convert back to actual value 

SELECT
 CONVERT(95000.75, 'UTF8', 'WE8EBCDIC500') mask_value,
 CONVERT(CONVERT(95000.75, 'UTF8', 'WE8EBCDIC500'),
                           'WE8EBCDIC500', 'UTF8') true_value
FROM DUAL
;