MySQL :: MySQL 8.4 Reference Manual :: 10.2.1.16 ORDER BY Optimization

Optimizing Subqueries, Derived Tables, View References, and Common Table Expressions Optimizing IN and EXISTS Subquery Predicates with Semijoin and Antijoin Transformations

[yife]

"By default, MySQL sorts all GROUP BY col1, col2, ... queries as if you specified ORDER BY col1, col2, ... in the query as well." MySQLではORDER BYを指定しないと、"GROUP BY col1, col2... ORDER BY col1, col2..."のように扱う

[abe_hn]

5.0のもチェック あんまり変わってない