SQL vs MySQL: Rules about aggregate operations and GROUP BY

Question

In this book I\'m currently reading while following a course on databases, the following example of an illegal query using an aggregate operator is given:

Answer 1

By the way, it is default MySQL behavior. But it can be changed by setting ONLY_FULL_GROUP_BY server mode in the my.ini file or in the session -

SET sql_mode = 'ONLY_FULL_GROUP_BY';
SELECT * FROM sakila.film_actor GROUP BY actor_id;

Error: 'sakila.film_actor.film_id' isn't in GROUP BY

ONLY_FULL_GROUP_BY - Do not permit queries for which the select list refers to nonaggregated columns that are not named in the GROUP BY clause.