Both Primary Key and Unique Key are used to enforce uniqueness of a column or a group of columns in a database table. However, there are some differences between them.
Primary Key:
A primary key is a column or a combination of columns that uniquely identify a record in a table. It cannot contain null values and there can be only one primary key per table. The primary key is automatically indexed by the database and is used as a foreign key in related tables to establish relationships between them.
Unique Key:
A unique key is a column or a combination of columns that must have unique values. Unlike primary keys, it can contain null values but there can be more than one unique key per table. A unique key is used to enforce the integrity of the data and ensure that there are no duplicate values in the table.
In summary, the main differences between Primary Key and Unique Key are:
- A table can have only one primary key, but can have multiple unique keys.
- A primary key cannot contain null values, but a unique key can contain null values.
- A primary key is used as a foreign key in other tables to establish relationships, while a unique key is used to enforce the integrity of the data and ensure that there are no duplicate values.
Both Primary Key and Unique Key are important in ensuring data integrity and should be carefully chosen based on the specific requirements of the database design.
