The internal level: internal schema or physical schema
– describes the physical storage structure of the database.
– describes the complete details of data storage and access paths
for the database.
• The conceptual level: conceptual schema or logical schema
– describes the structure of the whole database for a community of
users.
– hides the details of physical storage structures and concentrates
on describing entities, data types, relationships, user operations,
and constraints.
• The external or view level: external schemas or user views.
– Each external schema describes the part of the database that a
particular user group is interested in and hides the rest of the
database from that user group