" ...since there is so much confusion surrounding it in the industry. You will often hear claims to the effect that relational attributes can only be of very simple types (numbers, strings, and so forth). The truth is, however, that there is absolutely nothing in the relational model to support such claims. ...in fact, types can be as simple or as complex as we like, and so we can have attributes whose values are numbers, or strings, or dates, or times, or audio recordings, or maps, or video recordings, or geometric points (etc.).

The foregoing message is so important‒and so widely misunderstood‒that we state it again in different terms:

The question of what data types are supported is orthogonal to the question of support for the relational model. "

― , An Introduction to Database Systems