MySQL二级索引中，叶子节点上的主键是否有序？

Question

mysql index

In the MySQL secondary index, are the primary keys on the leaf nodes ordered?

Physical structure in MySQL secondary index

Answer 1

Modern versions of innodb implicitly add the primary key to all other keys. Eg index (foo) is actually index (foo,pk) . So different pk values will be in different leaf nodes (if I understand what you mean by that term).