- A.Supp
- B.Proj
- C.Part
- D.SP_P
正确答案及解析
正确答案
解析
从 “每个供应商可以为多个项目供应多种零件，每个项目可由多个供应商供应多种零件”中判断 SP_P 的联系类型是：多对多对多的关系。而选择供应商号和供应零件的数量只能从新的关系模式 SP_P 中选择査询条件 Where 与 Having 的区別： Where 是针对单条记录的判断条件，而 Having 是针对分组之后的判断条件。同时，由于考虑到项目号可能重复，所以要加 Distinct 去掉重复的项目。 ）
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