这篇文章是用英文写的，由于某种原因，这篇文章可以很直接的说是Anti-MongoDB一个和谐的DB（一）。写一的时候其实有很多问题，还是不很清楚的。所以有了以下的问题：
I has some questions about the nosql and the document database solutions because I just touch the nosql solutions these days,
I tried to understand and find the benefit of the NOSQL solutions (performance and scalability), but I cannot convince myself for the reasons, specially for the complex business related cases,
After read a lot of the articles and find the CAP, relational and Scalability are the three points for the NOSQL solutions,
CAP : only can pickup two of the three factors, and the NOSQL solutions pickup the AP, and use the eventually consistency to handle the consistency, now, let's check the RDBMS, if we have a lot of database servers, we also cannot have a good Consistency because of the performance issues, so we can choose the Master/Slave and asynchronize copy to handle the consistency (Similar with Eventually Consistency) which is similar with the NOSQL, so what is the benefit of the NOSQL (specify document database) from the CAP theory?
No-Relational object : the NOSQL is good at the no-relationship objects, for example, log. but log also can save to the RDBMS without relationship, so for the no-relationship objects, I think the mongo solution and the RDBMS solutions should be have the same performance and scalability. right?
Relational : in the mongodb.org there is a good example as following,
the address is embedded into the student which is reasonable and will make the performance better if we need load the address from the student in the UI, but the RDBMS also can do it for the 1-1 relationship, and the scores need ref to the another collection and which is also similar with the RDBMS and also need touch database two times when we load the course which also similar with RDBMS. so what is the benefit.
Partition and Sharding : RDBMS also provide the solutions (although need change some codes), and RDBMS also can handle them.