2016-01-18
yorkie opened this issue · comments
《数据库设计与关系理论》读书笔记
原始的关系模型有3个主要组件：结构、完整性和操作。
关系通常都是定义成表格形式？
After googling some results about "table and relationships", just got some articles from Microsoft Access Database, which is about documenting their user can create a relationship between tables.
Nothing more about why relations is usually defined in table form.
Type is the pool for valuing in every column in Database.
In relational database, selecting a master key usual operation, but not required.
Operations has the following cases:
- Restriction, namely query on where
- Projection, namely fields
- Production, namely joining
Relations is consists of elements and attributions, namely the rows and columns.
However the document-based database is only consists of document, namely the JSON/BSON object. We can group some documents into a collection, and put documents or BSON file under a same directory, now we call the directory a database in MongoDB.
Don't use relation system in normal simple method for saving and reading. (Why?)
Relation model's goal is to make system consider the performance, not users. (This sounds good, I thought the SQL has a slow performance)