A
database schema ( ) of a
database system is its structure described in a
formal language supported by the
database management system (DBMS). The term "schema" refers to the organization of data as a blueprint of how the database is constructed (divided into database tables in the case of
relational databases). The formal definition of a
database schema is a set of formulas (sentences) called
integrity constraints imposed on a database. These integrity constraints ensure compatibility between parts of the schema. All constraints are expressible in the same language. A database can be considered a structure in realization of the
database language. The states of a created
conceptual schema are transformed into an explicit mapping, the database schema. This describes how real-world entities are modeled in the database.