While the term schema is broadly used, it is commonly referring to three different schema types—a
conceptual database schema, a logical database schema, and a physical database schema.
Conceptual schemas offer a big-picture view of what the system will contain, how it will be organized,
and which business rules are involved. Conceptual models are usually created as part of the process of
gathering initial project requirements.
Logical database schemas are less abstract, compared to conceptual schemas. They clearly define
schema objects with information, such as table names, field names, entity relationships, and integrity
constraints—i.e. any rules that govern the database. However, they do not typically include any technical
requirements.
Physical database schemas provide the technical information that the logical database schema type
lacks in addition to the contextual information, such as table names, field names, entity relationships, et
cetera. That is, it also includes the syntax that will be used to create these data structures within disk
storage.
