which of the following describe situations where mongodb has a clear advantage over a typical relational database? check all apply
- developer need to get an application into production quickily
- Queries from applications are ad hoc and unpredictable
- The data model changes frequently
- Many Long running complex transactions are present
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由于mongodb是schema less的所以其初始开发速度异常的快， schema less意味着开发人员可以够少地做模式方案设计，更快将应用投产。
同时由于mongodb是schema less的，所以其数据模型变更几乎不需要做任何操作（alter table add/modify)。
对于ad hoc &unpredictable 特性的、无法预估的查询，mongodb对于字段搜索，范围查询、正则表达查询都支持。查询可以要求返回文件document的部分字段，同时也用上用户自定义的java script函数。
Ad hoc queries
MongoDB supports search by field, range queries, regular expression searches. Queries can return specific fields of documents and also include user-defined JavaScript functions. http://en.wikipedia.org/wiki/MongoDB
Many Long running complex transactions are present ==》 显然 mongodb中并不适合运行大的长的事务
