Introduction to Database-----Catalog and Schema

in SQL environment, both catalog and schema are abstract concepts, which are mainly used to solve naming conflicts.

a database system contains multiple catalog, each containing multiple schemas, each containing multiple database objects (tables, views, fields, etc.)

such as the fully qualified name of the database object table can be expressed as: Catalog name. Schema name. Table Name

The SQL standard does not require that the fully qualified name of each database object be unique, like a domain name, and that each IP address can have multiple domain names if you like.

from the point of view of implementation, the various database systems support and implementation of the catalog and schema vary widely, the simpler and most commonly implemented way is to use the database name as the catalog name, using the user name as the schema name, see the following table:

Suppliers	Catalog Support	Schema Support
Oracle	Not supported	Oracle User ID
Mysql	Not supported	Database name
MS SQL Server	Database name	the object belongs to the main name, and the 2005 version begins to change
DB2	when specifying a database object, the Catalog section omits	Catalog owner name
Sybase	Database name	The database belongs to the main name
Informix	Not supported	Don't need
Pointbase	Not supported	Database name

Introduction to Database-----Catalog and Schema