[Solved] Given tables authors(id, name) and books(author_id, title), what will this query return?SELECT a.name FROM authors a LEFT JOIN books b ON a.id = b.author_id WHERE b.author_id IS NULL; | SQL

SQL - LEFT and RIGHT JOIN

Given tables authors(id, name) and books(author_id, title), what will this query return?

SELECT a.name FROM authors a LEFT JOIN books b ON a.id = b.author_id WHERE b.author_id IS NULL;

AAuthors who have written at least one book

BAuthors who have not written any books

CAll authors regardless of books

DBooks without authors

Step-by-Step Solution

Solution:

Step 1: LEFT JOIN authors with books
All authors are included; books matched by author_id or NULL if none.
Step 2: Filter authors with no books
WHERE b.author_id IS NULL selects authors without any matching book.
Final Answer:
Authors who have not written any books -> Option B
Quick Check:
LEFT JOIN + NULL filter = authors without books [OK]

Quick Trick: LEFT JOIN + NULL in right table finds unmatched left rows [OK]

Common Mistakes:

MISTAKES

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