Oracle 11g Release 2

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CREATE TABLE "USER" ( UserID, UserPeers, Gender ) AS
SELECT 'Mike',  'Tom1, Bob1',   'M' FROM DUAL UNION ALL
SELECT 'John',  'Tom1, Greg1',  'M' FROM DUAL UNION ALL
SELECT 'Sally', 'Mike1, John1', 'F' FROM DUAL UNION ALL
SELECT 'Sara',  'Sally1, Bob1, TimTom1', 'F' FROM DUAL;
4 rows affected

CREATE TABLE special_user ( UserID ) AS
SELECT 'Tom1' FROM DUAL UNION ALL
SELECT 'John1' FROM DUAL 
2 rows affected

SELECT *
FROM   "USER" u
WHERE  EXISTS (
  SELECT 1
  FROM   special_user su
  WHERE  ', ' || u.userpeers || ', ' LIKE '%, ' || su.userId || ', %'
)


USERID
USERPEERS
GENDER


Mike
Tom1, Bob1
M

John
Tom1, Greg1
M

Sally
Mike1, John1
F