A unique identifier for each record in a database table is known as?

A primary key serves as the unique identifier for each record in a database table. It is a specific attribute or a combination of attributes that ensures each entry in the table can be uniquely identified, thus preventing duplicate records. This uniqueness is essential for maintaining data integrity and is a fundamental concept in relational database design.

The primary key also facilitates efficient retrieval of data, especially when other related tables are involved. It often serves as a reference point for foreign keys in other tables, establishing relationships between them. This is crucial for enforcing referential integrity, which ensures that relationships between tables remain consistent.

In contrast, a foreign key is used to establish a relationship between two tables but does not guarantee uniqueness within its own table. An index improves the speed of data retrieval but is not a unique identifier on its own. SQL commands are statements used to interact with the database, such as querying or updating data, rather than defining a unique identifier. Therefore, the primary key is the correct answer as it is specifically designed to uniquely identify records within a database table.