https://en.wikipedia.org/wiki/Pattern_matching https://baike.baidu.com/item/%E6%A8%A1%E5%BC%8F%E5%8C%B9%E9%85%8D

1、DDLDDL（Data Definition Language）数据库定义语言statements are used to define the database structure or schema. DDL是SQL语言的四大功能之