What is the difference between a clustered index and a non-clustered index in a database, and when would you use each?

1 Answers
Answered by suresh

Clustered Index vs. Non-Clustered Index in a Database

A clustered index is a type of index in a database that organizes the data rows in the table based on the order of the index key. This means that the physical order of the rows in the table matches the order of the index key. In other words, the data is sorted and stored in the table based on the values in the index key column.

On the other hand, a non-clustered index is a type of index in a database that does not affect the physical order of the data rows in the table. Instead, it creates a separate data structure that stores the index key values along with pointers to the corresponding rows in the table.

When to use each type of index:

  1. Clustered Index:
    • Use a clustered index when you need to physically sort and store the data rows in the table based on a specific column or set of columns.
    • Clustered indexes are ideal for columns that are frequently used for range queries, sorting, and grouping.
    • There can only be one clustered index per table, as it directly impacts the physical order of the data in the table.
  2. Non-Clustered Index:
    • Use a non-clustered index when you want to create additional access paths to the data without affecting the physical order of the rows in the table.
    • Non-clustered indexes are suitable for columns that are frequently used in search and join operations.
    • Multiple non-clustered indexes can be created on a table.

Understanding the differences between clustered and non-clustered indexes in a database is crucial for optimizing query performance and efficiently accessing data in various scenarios.

Answer for Question: What is the difference between a clustered index and a non-clustered index in a database, and when would you use each?