[Solved] Given tables Authors(id, name) and Books(id, author_id), what does this query return?SELECT name FROM Authors a WHERE EXISTS (SELECT 1 FROM Books b WHERE b.author_id = a.id); | SQL

SQL - Subqueries

Given tables Authors(id, name) and Books(id, author_id), what does this query return?

SELECT name FROM Authors a WHERE EXISTS (SELECT 1 FROM Books b WHERE b.author_id = a.id);

ANames of authors who have written at least one book

BNames of authors who have not written any books

CAll author names regardless of books

DNames of books written by authors

Step-by-Step Solution

Solution:

Step 1: Analyze the subquery
The subquery checks if there exists any book with author_id matching the author's id.
Step 2: Understand EXISTS behavior
EXISTS returns true if the subquery returns any rows, so the main query selects authors with at least one book.
Final Answer:
Option A -> Option A
Quick Check:
EXISTS filters authors having related books [OK]

Quick Trick: EXISTS checks for existence of related rows [OK]

Common Mistakes:

MISTAKES

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