We are Katie & Emil and together we have decided to learn more & more on how to build data warehouses using Microsoft products. The best option to learn is to teach so we write tutorials and share it with others.
In this blog psot we show how to restrict users from entering duplicated data by using SQL UNIQUE Constraint. In our examples we will use unique constraint on one field and we will use Email Address and one multiple fields and we will use First Name, Surname and Birth Date. This article has been written to support our SQL Tutorial and Exam Guide 70-461 Querying SQL Server 2012.