Clustered vs Non-Clustered Index in Database

When it comes to optimizing database performance, understanding the differences between clustered and non-clustered indexes is crucial for efficient database administration.

Clustered Index

A clustered index determines the physical order of data rows in a table. In a clustered index, the data rows are stored in the leaf nodes of the index in the same order as the index key.

Non-Clustered Index

A non-clustered index does not alter the physical order of the table rows. Instead, it creates a separate structure that points back to the original table rows based on the indexed columns.

Key Differences

• Clustered indexes define the actual order of data rows, while non-clustered indexes do not.
• Tables can have only one clustered index, which also organizes the table data, but multiple non-clustered indexes can be created on a table.
• Clustered indexes are generally faster for retrieval operations on the indexed columns compared to non-clustered indexes.
• Clustered indexes are ideal for range queries and sorting, while non-clustered indexes are better for individual row lookups and queries with JOIN operations.

It's important to carefully consider the use cases and requirements of your database when choosing between clustered and non-clustered indexes to optimize performance and efficiency.