转储中的 MySQL 标志

Question

查看 mySQL 转储时，我遇到了一些东西，想知道它们是什么。

我明白了:

/*!50001 DROP TABLE IF EXISTS `xxx` */;

flag 50001是什么意思，有什么意思的列表吗？

Answer 1

它在 MySQL 的论坛/邮件列表上进行了讨论 here .

/*!50001 DROP TABLE `category_count_view`*/; 

This is a "feature" of MySQL. Any other RDBMS will treat this as a comment.

But, MySQL looks at 50001 and checks that as a MySQL version. This is Version 5.00.01, or 5.0.1 in the real world, but leaves room for the the sub-version and release to be greater than 9.

MySQL will treat the line as a comment if MySQL is below 5.0.1, and will process the line if MySQL is greater than or equal to 5.0.1.

It's a way making a SQL script compatible with different versions of MySQL, and allows new features to be included.