铁路客运售票系统，实现售票，订票，退票功能-Railway passenger transport ticketing system, ticketing, booking, the refund function

铁路客运售票系统，实现售票，订票，退票等的概念模型、逻辑模型、物理模型的建模，及SQL语言的实现-Railway passenger ticketing system and ticketing, booking, a refund, such as the conceptual model, logical model, physical model, modeling, and the SQL language to achieve