WITH sample_SQL ( line#, txt ) AS ( 
SELECT line#, txt 
  FROM dual 
 MODEL DIMENSION BY (1 as line#) 
       MEASURES (cast(null as varchar2(50)) as txt) 
RULES 
( txt[1] = 'SELECT count(*) cnt -- comment type#1' 
, txt[2] = ' FROM dual /* comment type #2 */ table_alias' 
, txt[3] = ' WHERE 1 = 1 /* start multiline comment' 
, txt[4] = ' ... other comments here ...' 
, txt[5] = ' ... and more here ...' 
, txt[6] = ' ... end of comment */ AND 2 = 2' 
, txt[7] = ';' 
) ORDER BY line# 
), 
concat_SQL as ( 
SELECT listagg(txt,chr(10))within group(order by line#) txt 
  FROM sample_SQL 
), 
parms AS ( 
SELECT r#, pt, rr, dx 
  FROM dual 
 MODEL DIMENSION BY (1 as r#) 
       MEASURES(cast(null as varchar2(50)) as pt 
               ,cast(null as varchar2(50)) as rr 
               ,cast(null as varchar2(50)) as dx) 
RULES 
( pt[1] = '--.+'||chr(10)            , rr[1]=chr(10)      , dx[1]='double-dash' 
, pt[2] = '/\*(.|'||chr(10)||')*?\*/', rr[2]=''           , dx[2]='slash/asterisk' 
--, pt[3] = chr(10)                    , rr[3]=' -'||chr(10), dx[3]='COPY continued' 
)), 
rCTE (r#, txt, dx ) AS ( 
SELECT 0, txt, 'original' 
  FROM concat_SQL 
UNION ALL 
SELECT parms.r# 
     , REGEXP_REPLACE(rCTE.txt,parms.pt,parms.rr) 
     , parms.dx 
  FROM rCTE 
  JOIN parms 
    ON rCTE.r# + 1 = parms.r# 
) 
SELECT * 
  FROM rCTE 
 ORDER BY r#