What is a database schema?
A database schema is described in a formal language supported by
the database management system (DBMS). In a relational database,
the schema defines the tables, the fields in each table, and the
relationships between fields and tables. Schemas are generally
stored in a data dictionary. Although a schema is defined in text
database language, the term is often used to refer to a graphical
depiction of the database structure Levels of database schema
1. Conceptual schema, a map of concepts and their relationships
2. Logical schema, a map of entities and their attributes and
relations 3. Physical schema, a particular implementation of a
logical schema 4. Schema object, Oracle database object 5. Schema
is the over all structure of the database