Suppose we have a relation schema R(A, B, C) with FD A rightarrow B. Suppose also that we decide to decompose this schema into S
(A, B) and T(B, C). Give an example of an instance of relation R whose projection onto S and T and subsequent rejoining as in Section 3.4.1 does not yield the same relation instance. That is, pi_A, B(R) pi_B, C (R) notequalto R.
1 answer:
Answer:
Check the explanation
Explanation:
A relation schema is the fundamental schema for a table. Which is In a relational kind of database (what individuals naturally refer to when they talk about database) each take can be referred to as a "relation" . therefore a relational schema is the design for the table.
kindly check the attached image below to see the step by step solution to the question.
You might be interested in
Answer:
your answer is in the pic
(◔‿◔)
｡◕‿◕｡
Answer:
Check the explanation
Explanation:
Note : check attached image for output and program and also note that you're to replace "at" with shift 2 as the brainly text editor can't take the symbol
Program : **************Magzine.java**********************
/*
* To change this license header, choose License Headers in Project Properties.
* To change this template file, choose Tools | Templates
* and open the template in the editor.
*/
public class Magzine {
//class variable private can not access outside class
private String title;
private String month;
private int year;
//parameterized constructor
public Magzine(String title,String month,int year)
{
this.title=title;
this.month=month;
this.year=year;
}
//override toString method
"at"Override
public String toString()
{
String detail=title+" "+month+" "+Integer.toString(year);
return detail;//return string of class variable
}
//get Magzine objecte
public boolean equals(Magzine obj)
{
//commented returm statement compare string by address so you can uncomment if
//we do not use same string object of String class
//return this.month==obj.month && this.title==obj.title && this.year==obj.year;
//compare two object element if matches return true else false
return (this.month.equals(obj.month)) &&(this.title.equals(obj.title)) && this.year==obj.year;
}
}
Program : *************************Main.java****************************
/*
* To change this license header, choose License Headers in Project Properties.
* To change this template file, choose Tools | Templates
* and open the template in the editor.
*/
public class Main {
/**
* "at"param args the command line arguments
*/
public static void main(String[] args) {
// TODO code application logic here
Magzine Obj =new Magzine("Scientific American ", "April", 2020); //object of class
Magzine Obj1 =new Magzine("Scientific American ", "April", 2020);//Obj and obj1 is same content data
Magzine Obj2 =new Magzine("Scientific American", "June", 2020); //obj and obj1 same but obj2 different
System.out.println(Obj.toString()); //print string of obj
System.out.println(Obj1.toString());//print string of obj1
System.out.println(Obj2.toString());//print string of obj2
System.out.println(Obj.equals(Obj1)); //obj and obj1 equal and return true
System.out.println(Obj.equals(Obj2)); // obj and obj2 not equal so return false
}
}
Output can be seen below:
