单选

在某企业的工程项目管理系统的数据库中供应商关系Supp、项目关系Proj和零件关系Part的E-R模型和关系模式如下:

Supp(供应商号,供应商名,地址,电话)

Proj(项目号,项目名,负责人,电话)

Part(零件号,零件名)

其中,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。SP P需要生成一个独立的关系模式,其联系类型为( )

给定关系模式SP P(供应商号,项目号,零件号,数量)查询至少供应了3个项目(包含3项)的供应商,输出其供应商号和供应零件数量的总和,并按供应商号降序排列。

           SELECT  供应商号,SUM(数量) FROM( )

              GROUP BY 供应商号

             ( )

               ORDER BY 供应商号DESC;

  • A.*:*:*
  • B.1:*:*
  • C.1:1:*
  • D.1:1:1
  • A.Supp
  • B.Proj
  • C.Part
  • D.SP P
  • A.HAVING COUNT(项目号)>2
  • B.WHERE COUNT(项目号)>2
  • C.HAVING COUNT(DISTINCT(项目号))>2
  • D.WHERE COUNT(DISTINCT(项目号))>3
参考答案
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