What does it mean to say that a database displays both entity integrity and referential integrity? And why entity integrity and referential integrity important in a database? Provide an application example to support your discussion.
Sample Answer
Entity integrity and referential integrity are two important concepts in database design.
Entity integrity ensures that each row in a table is unique. This is done by assigning a primary key to each table, which is a column or a combination of columns that uniquely identifies each row in the table.
Referential integrity ensures that the foreign keys in a table point to valid values in the primary key of another table. This is done by creating a foreign key constraint on the foreign key column.
A database that displays both entity integrity and referential integrity is a well-designed database that is less likely to experience errors.
Full Answer Section
Here are some of the reasons why entity integrity and referential integrity are important in a database:
- To ensure data accuracy:Â Entity integrity ensures that each row in a table is unique, which helps to ensure that the data in the table is accurate.
- To prevent data loss:Â Referential integrity prevents orphaned rows, which are rows that have no corresponding rows in the table that the foreign key references. This helps to prevent data loss.
- To improve performance:Â Entity integrity and referential integrity can help to improve the performance of a database by preventing duplicate data and by ensuring that the data in the database is consistent.
- To simplify data management:Â Entity integrity and referential integrity can simplify data management by making it easier to insert, update, and delete data in the database.
Here is an example of how entity integrity and referential integrity can be used in an application:
Suppose we have a database of students and their courses. The student table would have a primary key of student ID, and the courses table would have a primary key of course ID. The courses table would also have a foreign key of student ID that references the student table. This would ensure that each student in the courses table is a valid student in the student table.
Without referential integrity, it would be possible to add a row to the courses table with a student ID that does not exist in the student table. This would create an orphaned row, which would be inaccurate and could lead to data loss.
By enforcing referential integrity, we can prevent this from happening and ensure that the data in our database is accurate and consistent.
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