Primaarvõtit

Primaarvõtit, often translated as primary key, is a fundamental concept in relational database management systems. It is a column or a set of columns that uniquely identifies each record in a database table. The primary key ensures that each row in the table can be unambiguously referenced and accessed.

There are several key characteristics of a primary key. Firstly, it must contain unique values; no two rows can have the same primary key. Secondly, it cannot contain NULL values. Each record must have a value for its primary key. These constraints are crucial for maintaining data integrity and preventing redundancy.

When designing a database, selecting an appropriate primary key is an important decision. Often, an integer column with an auto-incrementing value is used as a primary key, referred to as a surrogate key. Alternatively, one or more existing columns that naturally possess unique and non-null values can be chosen as a composite primary key or a natural key.

The primary key serves multiple purposes. It is used to establish relationships between different tables in a relational database through the use of foreign keys. It also optimizes data retrieval operations, as databases can efficiently locate specific records using their primary key. In essence, the primary key acts as the unique identifier for each entry within a database table.