Data integrity refers to the accuracy, consistency, and reliability of data in an information system, especially in a database. It ensures that data is correct and dependable, meeting the expected standards. Data integrity encompasses various aspects:

1. Uniqueness: Data integrity ensures that records in a database are unique and free from duplicates, often achieved through the use of primary keys, which guarantee each record has a unique identifier.

2. Completeness: Complete data integrity ensures that all necessary data is present in a database, with no missing values or empty fields.

3. Accuracy: Data must be correct and precise, reflecting real-world conditions or actual facts accurately.

4. Consistency: Data integrity ensures that data is consistent and does not contain conflicting information. Data related across different parts of the system or in different tables should be in harmony.

5. Integrity Rules: Databases can use integrity rules to enforce that entered data meets required criteria. For example, integrity rules can mandate that a specific date field contains a valid date.

6. Security: Data integrity also involves protection against unauthorized alterations or deletions of data. Security measures, such as permissions and access controls, are implemented to safeguard data from unauthorized access.

Maintaining data integrity is crucial for the reliable operation of information systems and databases as it ensures that the stored data is trustworthy and meaningful. Data integrity is a central concept in database management and data management in general.

A primary key is a concept in database management used to uniquely identify records in a database table. A primary key serves several important functions:

1. Unique Identification: The primary key ensures that each record in the table has a unique identifier, meaning no two records can have the same primary key value.

2. Data Integrity: The primary key ensures data integrity by preventing duplicates in the table, thus maintaining the consistency of the database.

3. Table Relationships: In relational databases, relationships can be established between different tables by using the primary key of one table as a foreign key in another table. This allows for data linking between tables and the execution of complex queries.

A primary key can consist of one or more columns in a table, but in many cases, a single column is used as the primary key. The choice of the primary key depends on the application's requirements and the nature of the database.

Common examples of primary keys include customer or employee IDs in a table, ensuring that each record in that table can be uniquely identified. A primary key can also include automatically generated values like sequential numbers or unique strings.