FAQ: What Are Database Relationships? - Many-to-Many Relationship Part 2

This community-built FAQ covers the “Many-to-Many Relationship Part 2” exercise from the lesson “What Are Database Relationships?”.

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This exercise can be found in the following Codecademy content:

Design Databases With PostgreSQL

FAQs on the exercise Many-to-Many Relationship Part 2

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What is the point of populating a many-to-many table like in this exercise? If ‘book’ and ‘author’ are populated, doesn’t ‘books_authors’ get populated?

The point is mapping the book to the author. An author can write many books, and a book can have many authors. The books to authors table will not get populated automatically if thats what you are asking.

Came here to say as someone that has been working in SQL for 20 years… I would suggest you do not write your code in this format as the exercise gives as an example. This is the old format that fell out of favor 15+ years ago. Use the explicit JOIN format.

SELECT column_one AS alias_one, column_two AS alias_two
FROM table_one, table_two, joined_table
WHERE table_one.primary_key = joined_table.foreign_key_one
AND table_two.primary_key = joined_table.foreign_key_two

Beyond looking old and outdated… the explicit JOIN method is much nicer for troubleshooting and performance tuning. You can quickly see which criteria is part of the join vs a filtering factor in the where.