Less common but possible is to have two or more materials in a single solid phase. A mixture can have two or more liquid or solid phases. Benzene and water form two separable liquid phases. Likewise a crystals of two different materials are two different solid phases. In fact, it is not always easy to identify a complete list of constituents.
Components are chemically independent constituents of a system.
These are both easier and more difficult to enumerate. For example, consider pure water. So while we might consider this to be three constituents, there is only one component in pure water. If we move on to the sodium chloride in water example, we now have possibly five constituents, but only two components. If no chemical reaction takes place, the number of components equals the number of constituents.