How to use index in select query in sql server

SQL indexes are data structures that allow for efficient retrieval of data from a database.

Types of indexes in sql

They are used to speed up queries and improve database performance by reducing the amount of data that needs to be scanned to find the desired information.

Indexes are created on one or more columns in a table, and they work by creating a separate data structure that contains a copy of the indexed data.

This data structure is organized in a way that allows for quick lookups, similar to an index in a book. When a query is executed that includes the indexed column(s), the database engine can use the index to quickly locate the relevant data.

There are several types of SQL indexes, including:

Clustered index: This type of index determines the physical order of the data in a table, based on the values of the indexed column(s).

Each table can have only one clustered index, and it is typically created on the primary key column(s) of the table.

Non-clustered index: This type of index creates a separate data structure that contains a copy of the indexed data, but does not affect the physica

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