suresh In a PostgreSQL database, the main difference between a primary key and a unique key lies in their intended functions and constraints.
Primary Key in PostgreSQL Database
A primary key is a column or a set of columns that uniquely identifies each row in a table. It enforces the uniqueness of values and ensures that every row has a unique identifier. A primary key column cannot contain NULL values and only one primary key constraint can be defined for each table. Additionally, a primary key automatically creates a unique index on the specified column(s).
Unique Key in PostgreSQL Database
A unique key constraint in PostgreSQL also ensures the uniqueness of values within a column or a set of columns. However, unlike a primary key, a unique key allows NULL values. This means that multiple rows can have NULL values in columns under a unique key constraint. A table can have multiple unique key constraints defined, but each constraint must have a unique name within the table.
In summary, a primary key uniquely identifies each row in a table and does not allow NULL values, while a unique key constraint also enforces uniqueness but permits NULL values.
For more insights on PostgreSQL database and its key constraints, stay tuned to our website for informative articles and guides.
Please login or Register to submit your answer