设有关系R(A,B,C) 和S(A,D,E,F),若将关系代数表达式:∏R.A,R,R.B,S.D,S.F(R∞S)用SQL语言的查询语句表示,则有:SELECTR.A,B,D,F FROMR,S WHERE 【 】。
For this part, you are allowed thirty minutes to write a composition on the topic: Clubs and Societies in a University. You should write at least 120 words following the outline given in Chinese.
1.大学里有各种各样的俱乐部和社团
2.俱乐部和社团应该发挥什么样的作用
3.我的看法