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Thursday, September 10, 2009

Database Integrity

Database Integrity is the preservation of data correctly & implies the process of keeping the dbase away from accidental deletion or alteration.
There are following types of integrity constraints:-
• Entity integrity constraints
• Referential integrity constraints
• Domain integrity constraints

DATABASE SECURITY: - Database security is a measurement of confidence that the integrity of a system and its data will be preserved.
Database security is assigned to address the following issues:-
• Privacy of data elements
• Preserving policies of organization
• System related security level
• Maintaining integrity of the database

Data integrity can be compromised in a number of ways:
- Human errors when data is entered.
- Errors that occur when data is transmitted from one computer to another.
- Software bugs or viruses.
- Hardware malfunctions, such as disk crashes.
- Natural disasters, such as fires and floods.

There are many ways to minimize these threats to data integrity. These include:
- Backing up data regularly.
- Controlling access to data via security mechanisms.
- Designing user interfaces that prevent the input of invalid data.
- Using error detection and correction software when transmitting data.

* Declarative Ease
Define integrity constraints using SQL statements. For these reasons, declarative integrity constraints are preferable to application code and database triggers. The declarative approach is also better than using stored procedures, because the stored procedure solution to data integrity controls data access, but integrity constraints do not eliminate the flexibility of ad hoc data access.
* Centralized Rules
Integrity constraints are defined for tables (not an application) and are stored in the data dictionary. Any data entered by any application must adhere to the same integrity constraints associated with the table.
* Maximum Application Development Productivity
If a business rule enforced by an integrity constraint changes, then the administrator need only change that integrity constraint and all applications automatically adhere to the modified constraint.
* Superior Performance
The semantics of integrity constraint declarations are clearly defined, and performance optimizations are implemented for each specific declarative rule.
* Flexibility for Data Loads and Identification of Integrity Violations
You can disable integrity constraints temporarily so that large amounts of data can be loaded without the overhead of constraint checking.
* The Performance Cost of Integrity Constraints
The advantages of enforcing data integrity rules come with some loss in performance.

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