add counter column in SQL query

Hello,

 I want to add counter column in below SQL query...  with below condition

   1. A counter number should be  same for same  logical_filename and when logical_filename value changed counter should be increase as per below example.

incomplete SQL

select                                            

    tit.test_instance_id   test_instance_id,                         

    tit.file_name  file_name,                                

    eb.logical_filename  logical_filename, 

   < add counter column here>                   

from                                              

    ec_blob eb,                                   

    test_info_tag_ext tit                         

where                                             

    tit.test_instance_id = eb.test_instance_id and

    tit.file_name = eb.real_filename 

    and tit.file_name='abc.trc'

order by tit.test_instance_id, tit.file_name, eb.logical_filename;