How to make two attribute unique

["piyush joshi" <joy.piyush@gmail.com>]

Hello All,

              I wanna know is it possible to make 2 attributes  unique Example -: mail and mailAlternateAddress , I mean to say if i have set abc@expmple.net in mail attribute as a value and if then I try to add same to the mailAlternateAddress attribute it will prevent me to do this and also  vice versa.

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Regards

Piyush Joshi
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