What is the unique identifier for each record in a table that ensures data integrity?

The primary key serves as the unique identifier for each record in a database table, ensuring that no two records can have the same key value. This uniqueness is essential for maintaining data integrity, as it allows for reliable identification and retrieval of each individual record. Without a primary key, it would be challenging to distinguish between different records, especially in cases where other fields may contain duplicate or similar values.

In a relational database, the primary key not only ensures that each record is distinct but also supports relationships between tables, as other tables can reference the primary key to establish connections. This capability is vital for organizing data in a structured manner and maintaining referential integrity.

While foreign keys establish relationships with primary keys in other tables, composite keys consist of two or more fields combined to form a unique identifier, and secondary keys are often used for indexing to speed up searching but do not guarantee uniqueness. Each of these alternatives plays a role in database management, but the primary key is specifically designated for ensuring that each record is uniquely identifiable within a table.