REGEX help in oracle 10g

Question

Hi,
I have to check for non-numeric at a particular location of the usernames in my database.
The usernames i am looking for are something like given below:
SAMCM1
SAMCM2
SAMCM3
SAMDM1
SAMEM1
There are other usernames which i dont want to list ..something like the ones given below:
SAM1CM1
SAM2CM2
SAM4CM3
SAM8DM1
SAM3EM1
How to can i achieve to get the results ( the one mentioned in my 1st listing) above using regex in oracle 10g,the one where i dont want the usernames containing a numeric value at the 4th position of the username.
I tried but not success ,partly because my knowledge of regex is very poor.
Regds,
Kunwar

Answer 1

WITH t AS (SELECT COLUMN_VALUE nm
             FROM TABLE (sys.odcivarchar2list ('SAMCM1',
                                               'SAMCM2',
                                               'SAMCM3',
                                               'SAMDM1',
                                               'SAMEM1',
                                               'SAM1CM1',
                                               'SAM2CM2',
                                               'SAM4CM3',
                                               'SAM8DM1',
                                               'SAM3EM1')))
SELECT nm
  FROM t
WHERE REGEXP_LIKE (nm, '^.{3}[^[:digit:]]')
NM
SAMCM1
SAMCM2
SAMCM3
SAMDM1
SAMEM1