SQL code copied to buffer

Task 16:

Using a covering index

The actor table has an index idx_actor_last_name on the last_name column. Which of the following queries can use this index as covering index?

select last_name, last_update from actor order by last_name desc;

select last_name, count(*) from actor group by last_name;

select distinct last_name from actor;

select last_name from actor order by last_update;

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Learning SQL: Generate, Manipulate, and Retrieve Data by Alan Beaulieu

Learning SQL: Generate, Manipulate, and Retrieve Data by Alan Beaulieu

As data floods into your company, you need to put it to work right away―and SQL is the best tool for the job. With the latest edition of this introductory guide, author Alan Beaulieu helps developers get up to speed with SQL fundamentals for writing database applications, performing administrative tasks, and generating reports. You’ll find new chapters on SQL and big data, analytic functions, and working with very large databases.

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