primærnøkler
A primary key is a column or a set of columns in a database table that uniquely identifies each row in that table. It ensures that the data in the table is unique and not duplicated. Primary keys are essential for maintaining the integrity of the data and for establishing relationships between tables in a relational database.
Primary keys have several key characteristics:
1. Uniqueness: Each value in the primary key column must be unique. No two rows can have
2. Non-nullability: Primary key columns cannot contain null values. Every row must have a valid primary key
3. Immutability: The value of a primary key should not change once it is set. This ensures
Primary keys are often used as foreign keys in other tables to establish relationships between tables. For
Primary keys can be of different types, including:
1. Simple primary key: A single column that uniquely identifies each row.
2. Composite primary key: A combination of two or more columns that together uniquely identify each row.
Primary keys play a crucial role in database design and management, helping to ensure data integrity, optimize