| 摘要 |
A database comprising: a polymorph table (Polymorph_assets) for a set of virtual tables (PCs,Cars,Phones) and a mapping structure (MTable). The polymorph table comprises: a discrimination column (Asset_type) for storing an identifier of the relevant virtual table and a total number of polymorphic columns of each data type equal to a maximum number of the virtual columns of the data type in the virtual tables. The mapping structure stores mapping information mapping each virtual column (a column in a virtual table) to a corresponding one of the polymorphic columns of the same data type. When the database receives a request for data in a virtual table the mapping structure is used to translate this request into a request for data from the polymorph table. |
