SQL – Data Definition - 4

System Tables…

• Whenever definition change occurs those activities will be recorded in the database.
• Those information are kept in tables known as system tables.
• Similar to the tables we created earlier but this will maintain only by the database itself.
• No user intervention is needed.
• This type of data is called meta data.

Schemas…

• Used to group database objects such as tables, views, stored procedures, etc
• Can be created using CREATE SCHEMA statement

Example…

• Create an academic schema and allow it access to the user, AccDiv
• CREATE SCHEMA Academic AUTHORIZATION AccDiv
• Then create the table Modules in this schema
• The name given to a table must be unique within the schema
• Same object name can be created in another schema
• DROP SCHEMA Academic

Catalogs…

• A catalog is a named group of schemas.
• Virtual one.
• There is no CREATE CATALOG statement.
• Each catalog should contain a schema called INFORMATION_SCHEMA which defines no.of views for system tables.
• INFORMATION_SCHEMA.TABLES
• INFORMATION_SCHEMA.COLUMNS