DatabasesBeginner
Primary Key
PronunciationPRY-meh-ree KEE
Definition
A primary key is a column or a set of columns in a database table that uniquely identifies each row. It ensures that no two rows have the same value in this field and that the value is never null.
Where you hear it
You hear this when designing database schemas, writing SQL queries, or configuring an ORM.
Examples
The
user_idcolumn is set as the primary key for the users table.Every table in the database must have a primary key to ensure data integrity.
Common mistake
Assuming that a primary key can contain duplicate values or nulls, which would break the fundamental rule of database uniqueness.