"Covering Indexes and Killing Lookups"

1. What is a covering index designed to do?

Speed up the query by minimizing the data retrieved from the table. Store a complete duplicate of the table. Only include the columns from the WHERE clause. Maximize the read costs on the database.

2. Which of the following columns should NOT be included in a covering index?

CustomerId Total OrderDate SELECT *

3. Why is it important to watch the width of a covering index?

Wider indexes lead to better performance. A wide index increases write costs and may approach the size of the base table. All indexes should be as wide as possible for efficiency. Narrow indexes are automatically optimally utilized.

4. What direct evidence can indicate that covering indexes would be beneficial?

High user scans and seeks User lookups on clustered index Low logical reads No equality predicates in queries

Continue: "Why Missing-Index Recommendations Mislead" → Review this lesson Retake quiz