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Data and structural independence
Structural Independence
Structural independence exists when changes in the database structure do not affect DBMS ability to access data.
Structural dependence exists when changes in the database structure do not affect DBMS ability to access data.
Data Independence
The changes done in the lower level will not affect the upper layers.
The two types are −
- Physical Data Independence
- Logical Data Independence
Let us begin with Physical Data Independence −
Physical Data Independence
Modify physical schema without affecting the schema or logical data. It is easier to achieve.
It is achieved by the internal level of the database and mapping from the logical level to the internal level. The Conceptual Schema from the changes done in the physical storage insulates the users.
Logical Data Independence
Modify logical schema without affecting the programs. It is hard to achieve. The conceptual schema can be modified without affecting the existing external schemas.
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