Loading subject…
Conceptual schema
The highest-level description of a database, naming the entities it must store and the relationships between them. It carries no attributes, keys, data types or storage detail.
Database schema
The structure of a database: the tables it holds, the attributes in each table, the relationships between them, and the constraints the data must obey. A schema defines organisation only and stores no records of its own.
Logical schema
A description of a database that adds every attribute, primary key and foreign key to the conceptual design. It stays independent of any particular database management system.
Physical schema
The lowest-level description of a database, fixing a data type and size for every attribute and specifying indexes, file organisation and storage structures for one chosen database management system.