What are the different types of indexes in SQL Server and explain when you would use each type in a database design?

Types of Indexes in SQL Server

In SQL Server, there are mainly four types of indexes:

1. Clustered Index: This type of index physically sorts and stores the data rows in the table based on their key values. It is recommended to use a clustered index on columns that are frequently searched or used for range queries.
2. Non-Clustered Index: A non-clustered index is a separate structure from the data table that contains pointers to the actual data rows. It is useful when searching for specific values and performing join operations.
3. Unique Index: A unique index ensures that the indexed columns do not contain duplicate values. It is suitable for enforcing data integrity constraints and improving query performance when searching for unique values.
4. Filtered Index: This type of index contains only a subset of rows in the table based on a filter condition. Filtered indexes are beneficial when querying a specific subset of data frequently.

When designing a database, you should consider the following scenarios to decide which type of index to use:

• Use a clustered index on columns frequently involved in range-based queries or sorting operations.
• Deploy non-clustered indexes on columns often used for searching, filtering, and joining tables.
• Employ a unique index to enforce uniqueness constraints on columns or when querying for distinct values.
• Utilize filtered indexes to index specific subsets of data based on query patterns.

By leveraging the appropriate types of indexes in SQL Server, you can optimize query performance and enhance the overall efficiency of your database design.