Clustered vs Non-Clustered

Index Selection: Clustered vs Non-Clustered

When you design your indexes, understanding your underlying data and their usage patterns is pivotal. If range queries are common and clustering similar data would give you a performance boost, a clustered index on a column like PersonId would be your go-to.

For unique or non-sequential columns, a non-clustered index can save the day — reducing insertion slowdown due to page splits and limiting fragmentation. However, for non-unique columns, including a uniqueifier may be necessary.

Performance Tuning through Index Design

Remember - when designing indexes, you'll have to balance the trade-offs between read and write operations. Key considerations for this balancing act include:

Sequential Keys: For clustered indexes, keys like INT or BIGINT identifiers that follow a sequence generally improve performance, while simultaneously preventing fragmentation on new data inserts.

Fill Factor Management: You can adjust fill factor settings to lessen page splitting for clustered indexes, taking into account the trends of your insert/update operations.

Included Columns with Non-key Values: Non-clustered indexes can carry included columns - this can improve query performance by resolving the query directly from the index itself.

The Balance: Selection and Insertion Performance

In the world of clustered indexes, you cannot ignore the impact of insert operations on performance. For instance, significant lock contention can occur if concurrent inserts are happening on the same page or if the clustered index key isn't chosen wisely.

A Balanced Solution:

• Compound Keys: A compound primary key as a clustered index covers selection efficiency, avoiding the need for uniqueifiers.
• Key Choices: While surrogate keys are often used for primary keys, they may not always be your first choice for clustered indexes.

Putting it All Together: Best Practices in Indexing

Experienced DBAs often tailor indexing strategies to specific use cases. Some practical approaches include:

Monitor Indexes: To manage logical fragmentation, periodically reorganize or rebuild indexes.

Performance Measurement: In a controlled environment, test different index structures to measure their impact on your workload.

Consult Authoritative Resources:: Use resources like MSDN and trusted community discussion forums to stay informed about the latest trends and best practices for indexing.