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Editor to share with you what data integrity in the computer network means, I believe that most people do not know much about it, so share this article for your reference, I hope you will learn a lot after reading this article. Let's learn about it!

Data integrity refers to: 1, domain integrity, that is, whether the input validity of a column is allowed to be null; 2, entity integrity, that is, ensuring that all rows in the table are unique; 3, referential integrity, that is, ensuring the reference relationship between the primary keyword (referenced table) and the external keyword (referenced table).

The operating environment of this tutorial: windows7 system, Dell G3 computer.

The state in which all data values stored in the database are correct. If incorrect data values are stored in the database, the database is said to have lost data integrity.

Data integrity (Data Integrity) refers to the accuracy (Accuracy) and reliability (Reliability) of data. It is proposed to prevent the existence of data that does not conform to the semantic provisions in the database and to prevent invalid operations or error messages caused by the input and output of error information.

Data integrity is divided into the following three categories:

(1) Domain integrity: refers to the input validity of a column and whether null values are allowed. Domain integrity is enforced by restricting the type (by setting the data type of the column), formatting (through CHECK constraints and rules), or the range of possible values (through FOREIGN KEY constraints, CHECK constraints, DEFAULT definitions, NOT NULL definitions and rules). For example, students' examination scores must be between 0100 and 100, and the gender can only be "male" or "female".

(2) entity integrity: means to ensure that all rows in the table are unique. Entity integrity requires that all rows in the table have a unique identifier. This unique identifier may be a column or a combination of several columns, called the primary key. That is, the primary key in the table must have a unique value on all rows. The methods to enforce entity integrity are: index, UNIQUE constraint, PRIMARY KEY constraint, or IDENTITY attribute. For example, the value of sno (student number) in the student table must be unique, it uniquely identifies the student represented by the corresponding record, and it is illegal to repeat the student number. The student's name cannot be used as the primary key, because it is entirely possible that two students have the same name and surname.

(3) referential integrity: refers to ensuring the reference relationship between primary keywords (referenced tables) and external keywords (referenced tables). It involves the consistency maintenance of the data of two or more tables. The foreign key value associates records in the reference table that contain additional keys and records in the referenced table where the primary key matches the foreign key. When entering, changing, or deleting records, referential integrity maintains defined relationships between tables and ensures that key values are consistent across all tables. Such consistency requirements ensure that non-existent values are not referenced, and if the key value changes, all references to that key value are changed consistently throughout the database. Referential integrity is based on the relationship between foreign keys and primary keys. For example, the course number for students to study the course must be a valid course number, and the foreign key cno (course number) of the score table (grade sheet) will refer to the primary key cno (course number) in the course table (course schedule) to achieve data integrity.

Domain integrity, physical integrity, and referential integrity are implemented on columns, rows, and tables, respectively. Data integrity can be implemented at any time, but when implementing data integrity on a table with existing data, the system must first check whether the data in the table meets the implemented integrity, and only the data in the table meets the implemented integrity. data integrity can be implemented successfully.

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