What is Postgres unique index?

What is an unique index?

Unique indexes are indexes that help maintain data integrity by ensuring that no rows of data in a table have identical key values. When you create a unique index for an existing table with data, values in the columns or expressions that comprise the index key are checked for uniqueness.

What is the difference between index and unique index?

Index: It is a schema object which is used to provide improved performance in the retrieval of rows from a table. Unique Index: Unique indexes guarantee that no two rows of a table have duplicate values in the key column (or columns).

What is the difference between primary and unique index?

Primary key will not accept NULL values whereas Unique key can accept NULL values. A table can have only one primary key whereas there can be multiple unique key on a table. A Clustered index automatically created when a primary key is defined whereas Unique key generates the non-clustered index.

What are the benefits of using a unique index?

Benefits of a Unique Index Provided that the data in each column is unique, you can create both a unique clustered index and multiple unique nonclustered indexes on the same table. Unique indexes ensure the data integrity of the defined columns.