What is unique index example?

What is unique index in SQL with example?

Multicolumn unique indexes guarantee that each combination of values in the index key is unique. For example, if a unique index is created on a combination of LastName, FirstName, and MiddleName columns, no two rows in the table could have the same combination of values for these columns.

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.

How do you create a unique index?

A unique index can be clustered or non-clustered. In this syntax: First, specify the name of the unique index after the CREATE UNIQUE INDEX keywords. Second, specify the name of the table to which the index associated and a list of columns that will be included in the index.

What is unique and non unique index?

UNIQUE refers to an index where all rows of the index must be unique. That is, the same row may not have identical non-NULL values for all columns in this index as another row.