What is a composite key in a relational database?
a) A key that consists of two or more columns used to uniquely identify a row
b) A key that is not unique
c) A key used to link multiple tables together
d) A key that is automatically generated by the database
Answer:
a) A key that consists of two or more columns used to uniquely identify a row
Explanation:
A composite key is a primary key that consists of two or more columns, which together uniquely identify a row in a table. Composite keys are used when no single column is sufficient to ensure uniqueness across the table.
For example, in an “orders” table, a composite key could consist of the “order_id” and “product_id” columns to uniquely identify each order for a specific product.
Composite keys are commonly used in many-to-many relationship tables where multiple columns are required to establish uniqueness.