Shulou(Shulou.com)06/01 Report--

The editor will share with you what are the redundancy problems in the database. I hope you will gain a lot after reading this article. Let's discuss it together.

Redundancy means that there are multiple copies of the same data in the database. This problem occurs when the database is well normalized. Suppose the student details attribute table is: student ID, student name, university name, university ranking, course selection.

It can be seen that the names of attribute colleges, university rankings, and the value of courses are being repeated, which can lead to problems. Problems caused by redundancy include inserting exceptions, deleting exceptions, and updating exceptions.

1. Insert exception

If student details must be inserted and their course has not been determined, it cannot be inserted until a time course is determined for the student.

This problem occurs if the data record cannot be inserted without adding some other extraneous data to the record.

two。 Delete exception

If you delete the details of the students in this table, then the details of the university will also be deleted, which should not be common sense.

This exception occurs when deleting a data record results in the loss of some irrelevant information stored as part of a record deleted from the table.

3. Update exception

Assuming a change in the level of the university, the change must be spread throughout the database, which will be time-consuming and expensive to calculate.

If no updates occur at all locations, the database will be in an inconsistent state.

After reading this article, I believe you have a certain understanding of the redundancy in the database, want to know more about it, welcome to follow the industry information channel, thank you for reading!

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