Features of Database schemas

• A database schema is a container that holds database objects such as tables or database views.
• Each database object belongs to a schema.
• A database schema acts as namespace for the database objects it contains
• A table or other objects present in a schema does not indicate ownership; the object is owned by its creator

 

 

 

Data Access Control

Relational database management systems, including SAP HANA, support the following basic ways for controlling which database user can access which data using SQL:

• Create database views that represent a portion of the data.
• Grant specific access permissions to selected users using the DCL of SQL.

 

DCL statements

GRANT: The GRANT statement is used to selectively grant access permissions to a user or role. Its basic syntax is:

GRANT <list of privileges> ON <database object> TO <user or role> [WITH GRANT OPTION]

 

 

 

 

REVOKE: This statement is used to selectively withdraw access permissions from a user or role. Its basic syntax is:

REVOKE <list of privileges> ON <database object> TO <user or role>

 

 

 

Database Indexes

A database index has the following properties:

• It can be considered an access path that helps the DBMS locate rows faster
• It can speed up searching and sort
• It has no influence on the result of queries, only on how fast the result is returned
• It can slow down INSERT, UPDATES and DELETE

 

 

 

 

Database index management

 

Create Index: This statement is used to create an index.

CREATE [UNIQUE] INDEX <index name> ON <table name> (<list of columns>).

 

 

DROP Index: This statement is used to delete an index. The underlying database table and its data are not deleted.

DROP INDEX <index name>