MySQL 8.4 Release Notes
MySQL 使用 锁定 来管理对表内容的争用：MySQL manages contention for table contents using locking:
内部锁定在 MySQL 服务器内部执行，以管理多个线程对表内容的争用。这种类型的锁定是内部的，因为它完全由服务器执行，并且不涉及其他程序。参见 第 10.11.1 节，“内部锁定方法”。Internal locking is performed within the MySQL server itself to manage contention for table contents by multiple threads. This type of locking is internal because it is performed entirely by the server and involves no other programs. See Section 10.11.1, “Internal Locking Methods”.
外部锁定发生在服务器和其他程序锁定
MyISAM表文件时，以协调各个程序何时可以访问这些表。参见第 10.11.5 节，“外部锁定”。External locking occurs when the server and other programs lockMyISAMtable files to coordinate among themselves which program can access the tables at which time. See Section 10.11.5, “External Locking”.