目录一、基本语法与默认行为1. 不指定默认值2. 显式设置默认值二、常用默认值设置方法1. 固定默认值（特定日期时间）2. 当前时间戳（插入时自动记录）3. 自动更新时间戳（记录修改时间）三
After keeping in mind that HTML has both an SGML and XML serialisations, which are just encodings for a parser to \"explode\" into a DOM, I\'m wondering whether there are other serialisations for HTML
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