The PRIMARY KEY constraint uniquely identifies each row in a table and must contain unique values.
A primary key is a column or a combination of columns that uniquely identifies each row in a table.
It ...read more

Question

The PRIMARY KEY constraint uniquely identifies each row in a table and must contain unique values.

A primary key is a column or a combination of columns that uniquely identifies each row in a table.
It ...read more

Accepted Answer

The PRIMARY KEY constraint uniquely identifies each row in a table and must contain unique values.

A primary key is a column or a combination of columns that uniquely identifies each row in a table.
It ensures data integrity by preventing duplicate or null values in the primary key column(s).
Primary keys are used to establish relationships between tables through foreign keys.
Primary keys can be composed of a single column or multiple columns.
Example: In a table of employees, the primary key could be the employee ID column.

The PRIMARY KEY constraint uniquely identifies each row in a table. It must contain UNIQUE values and has an implicit NOT NULL constraint. A table in SQL is strictly restricted to have one and only one primary key, which is comprised of single or multiple fields (columns)