the conception of schema is different in different db software.
here i just refer to oracle schema。
following is quote from "http://docs.oracle.com/cd/B19306_01/server.102/b14200/sql_elements007.htm"
schema conception:
Schema Objects
A schema is a collection of logical structures of data, or schema objects. A schema is owned by a database user and has the same name as that user. Each user owns a single schema. Schema objects can be created and manipulated with SQL and include the following types of objects:
Clusters
Constraints
Database
links
Database
triggers
Dimensions
External
procedure libraries
Index-organized
tables
Indexes
Indextypes
Java classes,
Java resources, Java sources
Materialized
views
Materialized
view logs
Object
tables
Object
types
Object
views
Operators
Packages
Sequences
Stored
functions, stored procedures
Synonyms
Tables
Views
Nonschema Objects
Other types of objects are also stored in the database and can be created and manipulated with SQL but are not contained in a schema:
Contexts
Directories
Parameter
files (PFILEs) and server parameter files
(SPFILEs)
Profiles
Roles
Rollback
segments
Tablespaces
Users
here we know that the database include schema objects and non-schema objects