由于DBI的局限和关系型数据库的广泛应用，Class： DBI在这一抽象中没有获得完全成功，但是它对90%的实际项目来说是足够的。
Because of the limitations of the DBI and relational databases in general, Class: : DBI is not completely successful in this abstraction, but it gets close enough for 90% of real-world projects.
在设计层次型数据库时，一个较好的设计方法是分二步走：首先利用实体联系方法抽象出现实世界的实体联系模型，然后将实体联系模型变换到具体DBMS 所支持的层次型模型。
A good algorithm to design such a hierarchical database consists of two steps, first, to describe real world in E-R model and then, convert it to the model supported by the DBMS.
在设计层次型数据库时，一个较好的设计方法是分二步走：首先利用实体联系方法抽象出现实世界的实体联系模型，然后将实体联系模型变换到具体DBMS 所支持的层次型模型。
A good algorithm to design such a hierarchical database consists of two steps, first, to describe real world in E-R model and then, convert it to the model supported by the DBMS.
应用推荐