What are table indexes ?

Indexes

• used for fast retrieval of information
• used to speed up query performance
• often created to the columns that are queried frequently

Types of Indexes

1. Clustered index 

• keeps all the records in the database in the order of clustered index key 
• There can be only one clustered index per table

2. Non-clustered indexes 

• stored as B-tree structure in their own storage (separate from data storage in the table)
• Logical order doesn’t match with physical order of stored data on disk
• There can be one or more Non-clustered indexes in a table