Database

Topics: Database, SQL, Database management system Pages: 3 (797 words) Published: October 6, 2014

1) Which account is designated as the owner of a relation? What privileges does the owner of a relation have? Ans: An "owner" account is given to those in control of specific relations. They have select, modification, and reference privileges on that given relation. 2) How is the view mechanism used as an authorization mechanism? Ans: A multiuser database system must selectively permit users to share data, while retaining the ability to restrict data access. There must be a mechanism to provide protection and security, permitting information to be accessed only by properly authorized users. Further, when tables or restricted views of tables are created and destroyed dynamically, the granting, authentication, and revocation of authorization to use them must also be dynamic. Each of these issues and their solutions in the context of the relational database management system System R are discussed. 3) Discuss the types of privileges at the account level and those at the relation level. Ans: The concept of an authorization identifier is used to refer, to a user account. The DBMS must provide selective access to each relation in the database based on specific accounts. There are two levels for assigning privileges to use the database system: l. The account level: At this level, the DBA specifies the particular privileges that each account holds independently of the relations in the database. 2. The relation (or table level): At this level, the DBA can control the privilege to access each individual relation or view in the database. The privileges at the account level apply to the capabilities provided to the account itself and can include the CREATE SCHEMA or CREATE TABLE privilege, to create a schema or base relation; the CREATE VIEW privilege; the ALTER privilege, to apply schema changes such adding or removing attributes from relations; the DROP privilege, to delete relations or views; the MODIFY privilege, to insert, delete, or update tuples; and the SELECT...
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