I have a table name specific. In this table are 2 fields named mainkey and no_in_row. A typical layout of the table would like like:

Mainkey                 No_in_row
JKT001                     10
JKT001                     20
JKT002                     10
JKT003                     10
JKT003                     20
JKT003                     30
JKT003                     30
JKT003                     40
JKT003                     40

Notice I can have duplicate mainkey's. The problem I have is that I need to detect whether I have duplicate No_in_row number for the same mainkey. Therefore I want to create an SQL to create a temp table which would show the following results based on the info above:

Mainey                   Duplicate           No_in_Row
JKT001                      No                   N/A
JKT002                      No                   N/A
JKT003                      Yes                   30
JKT003                      YES                   40

If there was a number of duplicates in each mainkey it would display the no_in row for each duplicate for the same mainkey.

Can anybody give me a some pointers

Many Thanks in Advance