Search a SQL server field for a creditcard number

creditCard.sql

SET ROWCOUNT 10000
SELECT SomeField
FROM   tablename
WHERE  patindex('%[3|4|5|6][0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9]%',SomeField) > 0 


or to get the unique numbers

SET ROWCOUNT 50
SELECT distinct  SUBSTRING (SomeField ,patindex('%[3|4|5|6][0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9]%',SomeField) , 12 )
FROM   tablename
WHERE  patindex('%[3|4|5|6][0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9]%',SomeField) > 0