Sleutelconstraints

Sleutelconstraints, often translated as key constraints, are a fundamental concept in relational database management systems. They are a type of integrity constraint that enforces the uniqueness and non-nullability of data within one or more columns of a table. These constraints are crucial for ensuring data accuracy, consistency, and reliability.

There are two primary types of key constraints: primary keys and unique keys. A primary key uniquely identifies each record in a table. It must contain unique values and cannot contain NULL values. A table can have only one primary key. A unique key also enforces uniqueness on a column or a set of columns, but unlike a primary key, it can allow for one NULL value if the column is nullable. A table can have multiple unique keys.

The purpose of sleutelconstraints is to prevent duplicate or meaningless entries, which could lead to data corruption or incorrect query results. When data is inserted or updated in a table, the database system checks if the proposed changes violate any defined key constraints. If a violation occurs, the operation is rejected, and an error message is typically returned. This proactive approach to data integrity is a cornerstone of relational database design.