Database System Achieving Referential Integrity Referential Integrity Referential integrity expresses that if a remote key exists in a connection, the estimation of the foreign key must coincide with the estimate of the essential key of some tuple in its main connection. Saves the characterized connection between relationships when records are included or deleted. It guarantees that the data in the two relationships are predictable.
Achieving Referential Integrity
Database System Referential integrity can be achieved by making the connection between the relationships the control In a relationship, one connection is called the primary connection and the other is called the daughter connection. The main connection contains the essential key and the youngest connection contains the remote key.
The referential integrity ensures the following:
- An estimate entered in the remote key field of the daughter connection must exist in the essential key field of the main connection.
- A record of a child’s connection cannot be deleted if there are coordination records in all 3 that could be against the main connection.
- The essential estimate of the key cannot be changed in the main connection if its comparative records exist in the young person’s connection.
A provision of the strategies used to keep the data updated is called file maintenance or data support. File support techniques incorporate including or changing records in the file or deleting records from the file.
- The record is included in the file when new data can be accessed. For example, when another substitute takes affirmation, the registration of the new substitute is included in the study file.
Change of records:
- The record in the file is changed for the reasons that accompany it.
To modify base data:
- suppose that the customer entered the wrong email of a substitute in the file by mistake. In case you need to rectify the email address, the current record will change.
To change existing data with new data:
- Suppose alternate changes his room The current address in the file progresses to become invalid, Therefore, the record must be modified to update the new address of the substitute.
- A record is deleted when it is no longer necessary. For example, when a substitute leaves the school, the record of that substitute is deleted from the study file.
The way of comparing data with a provision of principles or qualities to see if the data are rights called data approval Many projects carry out legitimacy checks or legitimacy principles to guarantee the accuracy of the data. For example, a legitimate email address must contain ‘@’ and the data approval improves its integrity before it is archived. Some legitimacy controls are the following:
Alphabetical verification ensures that the customer enters only the alphabetical data in a field hell guarantees that the client enters only numerical data in a field. For example, the Name field must be alphabetic and the data in the Impressions field must be numeric.
Verification of rank:
Range cheek decides if the number entered is within the predefined extension. In dir case, if the most important characteristics of a subject are 100, a range of care in the Imprints field guarantees that the data entered in the field is close to 0 and 100.
Verification of rank:
The consistency check tests the data to ensure that they are consistent, for example. The Date of Affirmation field must not contain a date before the current date. In addition, the incentive in the Date Limit field must not be before the incentive in the Confirmation Date field. I guess the number T used for the area.
Verification of consistency:
The consistency check ensures that the data in a field exists. This check prevents the client from leaving a cleared field. For example, a culmination monitors. The identification of the enlistment guarantees that the client has entered the registration number of the subordinate.
File processing system The file processing system was used by several associations to store and manage. The typical file processing system uses various file arrangements for each office in an organization. Records in a single file may not be identified with records stored in different files. the strategy of the files that we used in number 15 was used as 9.12.1 Types of File Association Pors.