Among the many database constraints available to us, the UNIQUE key constraint ensures the uniqueness of data in a column or a set of columns. Read on to find out more about the UNIQUE key constraint and how to define it in Vertabelo. In this article, we’ll focus on the UNIQUE key constraint. We’ll start with its basic definition and usage and gradually build up to more advanced options. Also, we’ll jump into Vertabelo and create an ER diagram that uses the UNIQUE key constraint.
Database schema migration is never an easy job. In fact, it can really be a headache, even when you’re working with a familiar system. For example, at times Oracle 10g may not drop the associated index for a primary key or unique constraint that has been dropped. In this article, I am going to explain when and why this happens. The Story: I’ve been working on the development of an e-commerce platform.
Sometimes there are columns in a table that don’t belong to primary key, but are still unique. To mark them as a unique, you have to create an alternate (unique) key containing it. Single-column alternate (unique) key Select the table with the column you want to make a unique. Then, click the Alternate (unique) key tab in the Table properties panel on the right: Click Add key: