I have a table with columns id,month,year,user_name,...etc in this table i want to make month,year and username unique.is it possible?IF it is ,please tell me, i required.

What database? For MySQL see here. Basically, it should look something like this, although you can specify more options:

CREATE UNIQUE INDEX MyIndex ON MyTable (month, year, username)

This is working.Thank you for your reply.

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