在基本表中,检索存储全部种类商品的仓库的编号及名称。试写出相应的关系代数表达式、元组表达式、关

Question

在基本表中，检索存储全部种类商品的仓库的编号及名称。试写出相应的关系代数表达式、元组表达式、关系逻辑规则和SELECT语句。

Answer 1

正确答案：关系代数表达式为： πS#.SNAME(STORE(πS#G#(SG)÷πG#(GOODS))) 元组表达式为： {t}((u)((v)((w)(STORE(u)∧GOODS(v)∧SG(w)∧w[1] =u[1)∧w[2]=v[1]∧t[1]=u[1]∧t [2]=u[2])} 关系逻辑规则如下： W(xy)← STORE(xya) ∧┑ GOODS(bc d) ∧┒ `SG(xbe) SELECT 语句为: SELECT S# SNAME FROM STORE WHERE NOT EXISTS ( SELECT * FROM GOODS WHERE NOT EXISTS ( SELECT * FROM SG WHERE SG. S# = STORE. S# AND SG. G# = GOODS. G#) );
关系代数表达式为： πS#.SNAME(STORE(πS#,G#(SG)÷πG#(GOODS))) 元组表达式为： {t}((u)((v)((w)(STORE(u)∧GOODS(v)∧SG(w)∧w[1] =u[1)∧w[2]=v[1]∧t[1]=u[1]∧t [2]=u[2])} 关系逻辑规则如下： W(x,y)← STORE(x,y,a) ∧┑ GOODS(b,c, d) ∧┒ `SG(x,b,e) SELECT 语句为: SELECT S#, SNAME FROM STORE WHERE NOT EXISTS ( SELECT * FROM GOODS WHERE NOT EXISTS ( SELECT * FROM SG WHERE SG. S# = STORE. S# AND SG. G# = GOODS. G#) );