sql - IBM Netezza, How to convert a varchar to a numeric with TO_NUMBER(..., ...) -

i have table called dart_stg1 in netezza database. table has varchar column. trying use below sql convert varchar number, throws error.

code

select distinct to_number(m12,'99g99')    dart_stg1   m12 not null; 

throws error:

error [hy000] error: bad numeric input format

what error mean?

the error:

error [hy000] error: bad numeric input format  

is caused because feeding letters to_number. feeding 99g99 not number.

the program tries tell it's not number telling numeric input format bad, error says.