Q:

Create db user with limited privileges

I have to create a sql 2008 database user that can backup and restore databases but NOT execute INSERT, UPDATE, DELETE.
Is it possible or the two operations are incompatible?

A:

You will need to assign them the role of db_BackupOperator to the login(s) to be able to do this.
They will be able to see the objects, but not the data in them or the code behind them.

