What is an unique index?

What is unique index 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 a unique index SQL?

SQL Server unique index overview A unique index ensures the index key columns do not contain any duplicate values. A unique index may consist of one or many columns. If a unique index has one column, the values in this column will be unique.

What is 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 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.