Database constraints help us keep our data clean and orderly. Let’s look at the most common database constraints and how to conveniently define them in Vertabelo. It’s a common practice to set rules for the data in a database. Thanks to these rules, you can avoid incorrect data in a column, e.g. a text string in an Age column or a NULL in a Name column. In this article, we’ll dive into SQL’s database constraints: PRIMARY KEY, FOREIGN KEY, NOT NULL, UNIQUE, DEFAULT, and CHECK.