There are three types of indexes -.
• Unique Index.
This indexing does not allow the field to have duplicate values if the column is unique indexed. Unique index can be applied automatically when primary key is defined.
• Clustered Index.
This type of index reorders the physical order of the table and search based on the key values. Each table can have only one clustered index.
• NonClustered Index.
NonClustered Index does not alter the physical order of the table and maintains logical order of data. Each table can have 999 nonclustered indexes.