设计模式不必多，只要掌握其中关键的几个，再结合实际的业务需求，一个完整的数据库模型就可以推导出来。 这里主要介绍给大家的是四种主要必备的设计方案。 -Design patterns do not need to, as long as the master key of a few, combined with the practical business needs, a complete database model can be derived. Here we are introdu