Delete rows and rownum

[John Putnam]

I have a case where Oracle's rownum would be great so I am looking for a MYSQL approach

The problem:

Bad records in a file of the form

unique_record key_field,grouping_field ..., Sequence_number

...

123 , 454 .... 1
124 , 454 .... 2
125, 454 .... 2
126, 454 .... 2
127, 679 .... 1
128, 679 .... 2
129, 679 .... 2
130, 897 .... 1

...

I need to delete all but one of the extra 2's so the end result is:

...

123 , 454 .... 1
124 , 454 .... 2
127, 679 .... 1
128, 679 .... 2
130, 897 .... 1

...

I am using Toad for MYSQL and want an SQL solution if possible.

Thanks,

John Putnam