The PRIMARY KEY constraint uniquely identifies each record in a table.
It does not allow duplicate values.
It also does not allow NULL values.
Every table should have one primary key.
It ensures each row can be identified uniquely.
Primary keys improve data organization.
A primary key can be created on a single column or a combination of columns.
It enforces uniqueness automatically.
PRIMARY KEY combines NOT NULL and UNIQUE behavior.
Only one primary key is allowed per table.
It is the most important constraint.
Primary keys are essential for table relationships.
They are used by foreign keys.
Understanding primary keys is mandatory for database design.