Composite key, also known as composite primary key or composite index, is a type of database index made up of multiple columns in a table that are used to uniquely identify a single row. Unlike the traditional single-column primary key, composite keys offer more control and flexibility in data storage.
Composite keys are created by combining two or more columns which together form a unique key, meaning it only appears once in a table. For example, one could create a composite key from a student’s first and last names to form a unique identifier for that student’s records.
Emphasis is placed on the combination of these columns that form the key, which means that the order in which columns are listed matters. For instance, a composite key made up of the student’s first and last names is different from the same two columns reversed and would therefore produce a different key.
Composite keys are used to enforce the unique values of the columns that make it up and can be used in a variety of applications. They can be used to enforce a relationship between more than two tables in a database, to form relationships between tables or simply to help identify a particular record from a table.
Composite keys are not without their drawbacks. Generally, they require more space and processing power since each key is larger than single-column primary keys. Additionally, composite keys are more vulnerable to the consequences of data entry errors than their single-column counterparts.
In conclusion, composite keys are an important tool that can be used in a wide variety of applications. They offer flexibility and control when designing data tables and managing relationships between tables, however they can increase the processing power and storage space required as well as making them vulnerable to human error. When designing a database, it is important to consider the benefits and drawbacks of all the options available before making a decision.
