>if there is a way to search a word or string in all fields
>in a table.

Yes, you can do that in a number of ways. For example

SELECT mytable
SCAN
  FOR i=1 TO FCOUNT()
    IF TYPE(FILED(i)) = "C"
       IF lcSearchDFor $ EVAL(lcUserName)
         *  Found, do something
       ENDIF
    ENDIF
  ENDFOR
ENDSCAN