In an RDBMS, what is a primary key?
- A key used for encryption
- A key used for foreign key constraints
- A key used for sorting data
- A unique identifier for a row in a table
In an RDBMS, a primary key is a column or set of columns that uniquely identifies each row in a table. It ensures the uniqueness of rows and provides a way to reference individual rows in the table. Primary keys are crucial for maintaining data integrity and enforcing entity integrity constraints. Typically, primary keys are indexed to facilitate fast data retrieval and enforce uniqueness.
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