Hi Sergiy, firstly thanks to you and everyone else who responded to my post.

I think I should rather have named the title of my post:

How to find duplicates based on 3 fields ? (being IDNo, Tel1, Tel3 - for Student)

Your script/sql query worked ok in some instances, but in some cases excluded some students, due to Tel3 / Tel1 / IDNo. What makes writing a query for such an issue difficult is that sometimes all 3 (IDNo, Tel1, Tel3) have values, in other cases only 2 of the 3 have values, in other only 1, in other none have a value. To add more pain to the issue, first instance of IDNo / Tel1 / Tel3 for student Jack might be identical to 2nd instance of Jack, the 3rd instance they might all differ, 4th instance some might differ.

Perhaps I should just use a cte -

Student, Tel1 for 1st query.

Then Student, Tel3 for 2nd query.

Then Student, IDNo for 3rd query.

Then join all 3 together, and hope it does the job.