为什么mySQL能够在通常无法重用别名时解析这些列别名？

Most SQL experts would say one can't re-use an alias in a select at the same level; often to work around this a CTE is used; or one wraps the query as a subquery so the alias can be referenced. However, mySQL seems to allow such a situation provided the alias is referenced in a Most SQL experts would say one can't re-use an