part3.txt

来自「ssd7 exercise2 答案」· 文本 代码 · 共 29 行

question 1:
 Table r  
  A B C 
  a b c 
  d a f 
  c b d 


 Table s 
  D E F 
  b g a 
  d a f 
 

s - r is a table whose tuples are members of s but not of r.
 

    Table s-r
    D  E  F
    b  g  a


question 2:
将表 MEMBER和BOOK作笛卡尔积得到一张新表，选出满足MemNo = BorrowerMemNo条件
及CallNumber = 'QA76.9.D26C66'条件但不满足CallNumber = 'QA76.9.D7E53'条件的
MemNo属性列。