[Solved] Which of the following best defines a covering index in a relational database? — Ans: An index that includes all columns needed to satisfy a query without accessing... | SQL

SQL - Indexes and Query Performance

Which of the following best defines a covering index in a relational database?

AAn index that only stores primary key values for faster lookups

BAn index that includes all columns needed to satisfy a query without accessing the table data

CAn index that covers all tables in a database schema

DAn index that automatically updates statistics for query optimization

Step-by-Step Solution

Solution:

Step 1: Understand the concept of covering index
A covering index contains all columns required by a query, so the database engine can retrieve results directly from the index without reading the table rows.
Step 2: Evaluate options
An index that includes all columns needed to satisfy a query without accessing the table data correctly describes this. Options B, C, and D describe unrelated or incorrect concepts.
Final Answer:
An index that includes all columns needed to satisfy a query without accessing the table data -> Option B
Quick Check:
Covering index = all needed columns in index [OK]

Quick Trick: Covering index contains all query columns [OK]

Common Mistakes:

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Which of the following best defines a covering index in a relational database?