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Authors:
Elmasri Navathe
Chapter:
Data Modeling Using The Entity–relationship (er) Model
Exercise:
Review Questions
Question:1 | ISBN:9780133970777 | Edition: 7

Question

Difference between logical data independence and physical data independence

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Answer

Logical data independence and physical data independence are two concepts in the field of database management systems.

Here's the difference between the two:

Logical Data Independence:

  • Logical data independence refers to the ability to modify the logical structure or organization of a database without affecting the external schema or application programs that depend on the database.
  • In other words, changes made to the logical representation of data, such as adding or modifying tables, attributes, or relationships, should not require modifying or recompiling the application programs that use the database.
  • This allows for flexibility and ease of maintenance, as modifications can be made at the logical level without disrupting the applications that rely on the database.
  • For example, suppose a database has a table called "Customers" with columns like "Name," "Address," and "Phone." If the database administrator decides to add a new column, such as "Email," to the "Customers" table, logical data independence ensures that existing application programs accessing the "Customers" table continue to function without any modifications.

Physical data independence:

  • Physical data independence refers to the ability to modify the physical storage or implementation details of a database without affecting the logical schema or external applications.
  • It allows changes to the physical storage structures, such as file organization, indexing techniques, or hardware upgrades, without impacting the way data is viewed or accessed by applications. Applications should remain unaffected by changes in the physical storage or hardware infrastructure.
  • For example, if the database administrator decides to migrate the database from one storage system to another or reorganize the file structure for performance improvements, physical data independence ensures that the application programs can continue to operate without any modifications.
  • The changes made at the physical level should not impact the logical representation of the data and the way applications interact with it.
  • In summary, logical data independence deals with changes made to the logical structure of the database, while physical data independence deals with changes made to the physical storage and implementation details.
  • Both concepts aim to provide flexibility and maintainability in database systems, allowing for modifications at different levels without disrupting the external applications that rely on the data.
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