st: how to find out observations that id variables can't uniquely identify?

[Nina YIN <yinnina.ccer@gmail.com>]

Dear all,

I want to merge two large datasets, before I merge them, I checked
whether id variables(applno productno) uniquely identify observations:
"by applno productno:assert _N==1", it turns out "4 contradictions in
26586 by-groups ", then I want to figure out what's the problem with
these 4 contradictions. However I don't know how to find out where
they are? Do you have any suggestions? Thanks a lot!



-- 
Best Regards,
Nina YIN


Toulouse School of Economics
Manufacture des Tabacs
21 Allee de Brienne
Toulouse, 31000, France
Tel: 0033-(0)5 6123 8348
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