【单选题】SQL语言是一种(96)语言,其主要功能有(97),它的典型句型为; SELECT A1,A2,...An FROM R1,R2,...Rm WHERE F 其中Ai(i=1,2,…,n)、Rj(j=1,2,…,m)和F分别是(98)。 关系模式学生成绩表(S#,C#,Score)中S#是学生的学号,C#是课程号,Score是学号为S#学生的C#号课程的成绩。若要查询每门课程的平均成绩,且要求查询...
【单选题】M: I don ’ t want to work with Tom. W: Why? It seems he always has good ideas. M: That ’ s the reason. He only uses his mouth, but I have to do all the hard work. Why doesn ’ t the man want to work wi...