Questions

Candidate Key – A Candidate Key can be any column or a combination of columns that can qualify as unique key in database. There can be multiple Candidate Keys in one table. Each Candidate Key can qualify as Primary Key. 

Primary Key – A Primary Key is a column or a combination of columns that uniquely identify a record. Only one Candidate Key can be Primary Key.

• One needs to be very careful in selecting the Primary Key as an incorrect selection can adversely impact the database architect and future normalization. For a Candidate Key to qualify as a Primary Key, it should be Non-NULL and unique in any domain.

The absence of a landmass within these latitudes in the southern hemisphere eliminate friction and lends force to these winds and hence derives the name

#include "string.h"

#include "stdlib.h"

struct stud

{

       int rollno;

       int marks;

       char name[30];

};

int sort_m (struct stud *, struct stud *);

int sort_name (struct stud *, struct stud *);

int sort_marks (struct stud *, struct stud *);

main()

{

static struct stud ss[] = {

                                            { 15, 96, "Akshay" },

                                            { 2, 97, "Madhuri" },

                                            { 8, 85, "Aishvarya" },

                                            { 10, 80, "Sushmita" }

                                   };

int x,w;

clrscr();

w = sizeof (struct stud);

printf ('\nIn order of roll numbers:");

qsort (ss, 4, w, sort_rn);

for(x=0; x<4;x++)

     printf ("\n%d%s%d", ss[x].rollno, ss[x].name,ss[x].marks);

printf("\n\nIn order of names:");

qsort(ss, 4, sort_name);

for (x=0; x<4;x++)

      printf("\n%d%s%d",ss[x].rollno, ss[x].name,ss[x].marks);

printf("\n\nIn order of marks:");

qsort(ss,4,w,sort_marks);

for (x=0;x<4;x++)

      printf ("\n%d%s%d",ss[x].rollno,ss[x].name,ss[x].marks);

}

int sort_rn (struct stud *t1, struct stud *t2)

{

     return (t1->rollno-t2->rollno);

}

int sort_name (struct stud *t1, struct stud *t2)

{

     return (strcmp(t1->name,t2->name));

}

int sort_marks (struct stud *t1, struct stud *t2)

{

     return (t2->marks-t1->marks);

}

Goa

The chemical element gold has an atomic number 79 is present in period 6 and group 11 of the periodic table.

In the first figure, number of triangles are 5.

In the second, the figure becomes double then the number of triangles also doubles.

i.e, 10.