WITH a AS
(
SELECT 'a,b,c,d,e' tag FROM dual
UNION ALL SELECT 'x,y,z' FROM dual
)
, b AS
(
SELECT 'c,d,e,f' tag FROM dual
)
SELECT a.tag
     , REGEXP_COUNT( ','||REPLACE(a.tag, ',', ',|,')||','
                   , ','||REPLACE(b.tag, ',', ',|,')||','
                   ) match_cnt
     , TRIM(BOTH ',' FROM
       REGEXP_REPLACE(
       REGEXP_REPLACE( ','||REPLACE(a.tag, ',', ',|,')||','
                     , '(,'||REPLACE(b.tag, ',', ',|,')||',)|.'
                     , '\1')
                     , ',+', ',')
                     ) match_tag
     , b.tag
  FROM a
     , b
 WHERE REGEXP_LIKE( ','||REPLACE(a.tag, ',', ',|,')||','
                  , ','||REPLACE(b.tag, ',', ',|,')||','
                  )
;

 감사합니다 ^^