In the SQL environment, both Catalog and Schema are abstract concepts. They are mainly used to solve naming conflicts. A database system contains multiple Catalog, and each Catalog contains multiple schemas, each Schema contains multiple database objects (tables, views, fields, and so on). For example, the fully qualified names of database object tables can be expressed as Catalog names. schema name. table Name SQL
In the SQL environment, both Catalog and Schema are abstract concepts. They are mainly used to solve naming conflicts. A database system contains multiple Catalog, and each Catalog contains multiple schemas, each Schema contains multiple database objects (tables, views, fields, and so on). For example, the fully qualified names of database object tables can be expressed as Catalog names. schema name. table Name SQL
In the SQL environment, both Catalog and Schema are abstract concepts. They are mainly used to solve naming conflicts.
A database system contains multiple Catalog, and each Catalog contains multiple schemas. Each Schema contains multiple database objects (tables, views, fields, and so on)
For example, the full 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 names of each database object be unique, just like domain names. If you like it, each IP Address can have multiple domain names.
From the perspective of implementation, the support and implementation methods for Catalog and Schema vary widely in various database systems. A simple and common implementation method is to use the database name as the Catalog name, use the username as the Schema name. For details, see the following table:
Supplier |
Catalog support |
Schema support |
Oracle |
Not Supported |
Oracle User ID |
MySQL |
Not Supported |
Database Name |
Ms SQL Server |
Database Name |
The object owner name, which has changed since version 2005. |
DB2 |
The Catalog part is omitted when the database object is specified. |
Catalog owner name |
Sybase |
Database Name |
Database owner name |
Informix |
Not Supported |
No |
PointBase |
Not Supported |
Database Name |