Thursday, December 20

Differences between GROUP BY and COMPUTE




The following summarizes the differences between COMPUTE and GROUP BY:



  • GROUP BY produces a single result set. There is one row for each group containing only the grouping columns and aggregate functions that show the sub-aggregate for that group. The select list can contain only the grouping columns and aggregate functions.

  • COMPUTE produces multiple result sets. One kind of result set contains the detail rows for each group containing the expressions from the select list. The other type of result set contains the sub-aggregate for a group, or the total aggregate for the SELECT statement. The select list can contain expressions other than the grouping columns or aggregate functions. The aggregate functions are specified in the COMPUTE clause, not in the select list.

Compute and Compute By Clause- SQL

Compute Clause:

It produces multiple result sets. One kind of result set contains the detail rows for each group containing the expressions from the select list. The other type of result set contains the sub-aggregate for a group, or the total aggregate for the SELECT statement. The select list can contain expressions other than the grouping columns or aggregate functions. The aggregate functions are specified in the COMPUTE clause, not in the select list.


Compute By Clause:

It can be used to calculate summary values of the result set on a group of data. The column name by which the data should be grouped is mentioned after BY keyword. The Group By clause produces group summary report, while Compute and Compute By produces summary report with individual data rows from table

Syntax of Compute:

SELECT Column_names
FROM Table_name
Order By Column_name(s)      //use only when need
COMPUTE aggregate_function(column_name)  //more than one 
                     aggregate_function(column_name) can be added

Syntax of Compute By:

SELECT Column_names
FROM Table_name
Order By Column_name(s)      //use only when need
COMPUTE aggregate_function(column_name)  //more than one
                     aggregate_function(column_name) can be added
BY Column_name(s)


**Order By column_name specifies the name of the column(s) by which data to be sorted in the result set.

**Compute aggregate_function specifies aggregate function that to be done on the row

**column_name specifies the name of the column for which the summary reports has to be produced

**By column_name(s) specifies the name column(s) by which data is to grouped.

Thursday, December 13

Program to count number of lines in a file


Write a program to find the number of lines in a text file.

Number of lines in a file can be determined by counting the number of new line characters present.

Program: Program to count number of lines in a file.

#include <stdio.h>
int main()
/* Ask for a filename and count number of lines in the file*/
{

//a pointer to a FILE structure
FILE *fp;
int no_lines = 0;

//consider 40 character string to store filename

char filename[40], sample_chr;

//asks user for file name
printf("Enter file name: ");

//receives file name from user and stores in a string named 'filename'

scanf("%s", filename);
//open file in read mode
fp = fopen(filename, "r");
//get character from file and store in sample_chr
sample_chr = getc(fp);
while (sample_chr != EOF) 
{
//Count whenever sample_chr is '\n'(new line) is encountered
if (sample_chr == '\n')
{
//increment variable 'no_lines' by 1
no_lines=no_lines+1;
}
//take next character from file.
sample_chr = getc(fp);
}
fclose(fp); //close file.
printf("There are %d lines in %s \n", no_lines, filename);
return 0;
}

Output:
Enter file name:abc.txt
There are 4 lines in abc.txt

Explanation:
In this program, name of the file to be read is taken as input. A file by the given name is opened in read-mode
using a File pointer 'fp'. Characters from the file are read into a char variable 'sample_chr' with the help of getc
function. If a new line character('\n') is encountered, the integer variable 'no_lines' is incremented. If the
character read into 'sample_char' is not a new line character, next character is read from the file. This process is
continued until the last character of the file(EOF) is encountered. The file pointer is then closed and the total
number of lines is shown as output.

Program for accepting a number in a given range


Write a C program which asks the user for a number between 1 to 9 and shows the number. If the user inputs a number out of the specified range, the program should show an error and prompt the user for a valid input.

Program: Program for accepting a number in a given range.

#include<stdio.h>
int getnumber();
int main() 
{
int input = 0;
//call a function to input number from key board
input = getnumber();
//when input is not in the range of 1 to 9,print error message
while (!((input <= 9) && (input >= 1))) 
{
printf("[ERROR] The number you entered is out of range");
//input another number
input = getnumber();
}
//this function is repeated until a valid input is given by user.
printf("\nThe number you entered is %d", input);
return 0;
}
//this function returns the number given by user
int getnumber() 
{
int number;
//asks user for a input in given range
printf("\nEnter a number between 1 to 9 \n");
scanf("%d", &number);
return (number);
}

Output:
Enter a number between 1 to 9
45
[ERROR] The number you entered is out of range
Enter a number between 1 to 9
4
The number you entered is 4

Explanation:
getfunction() function accepts input from user. 'while' loop checks whether the number falls within range or not
and accordingly either prints the number(If the number falls in desired range) or shows error message(number is
out of range).

Multiplication Table


Write a C program to display the multiplication table of a given number.

Program: Multiplication table of a given number

#include <stdio.h>
int main() 
{
int num, i = 1;
printf("\n Enter any Number:");
scanf("%d", &num);
printf("Multiplication table of %d: \n", num);
while (i <= 10) {
printf("\n %d x %d = %d", num, i, num * i);
i++;
}
return 0;
}

Output:
Enter any Number:5
5 x 1 = 5
5 x 2 = 10
5 x 3 = 15
5 x 4 = 20
5 x 5 = 25
5 x 6 = 30
5 x 7 = 35
5 x 8 = 40
5 x 9 = 45
5 x 10 = 50

Explanation:
We need to multiply the given number (i.e. the number for which we want the multiplication table)
with value of 'i' which increments from 1 to 10.

Friday, December 7

Concatenate Two Strings


Write a C program to concatenate two strings without using strcat() function.

strcat(string1,string2) is a C standard function declared in the header file string.h
The strcat() function concatenates string2, string1 and returns string1.

Program: Program to concatenate two strings

#include<stdio.h>
#include<string.h>
char *strct(char *c1, char *c2);
char *strct(char *c1, char *c2) 
{
        // strlen function returns length of argument string
int i = strlen(c1);
int k = 0;
        // loops until null is encountered and appends string c2 to c1
while (c2[k] != '\0') 
{
c1[i + k] = c2[k];
k++;
}
return c1;
}
int main() 
{
char string1[15] = "first";
char string2[15] = "second";
char *finalstr;
printf("Before concatenation:" " \n string1 = %s \n string2 = %s", string1, string2);

//addresses of string1, string2 are passed to strct()
finalstr = strct(string1, string2);
printf("\nAfter concatenation:");

//prints the contents of string whose address is in finalstr
printf("\n finalstr = %s", finalstr);

printf("\n string1 = %s", string1);     // prints the contents of string1

printf("\n string2 = %s", string2);    // prints the contents of string2
return 0;
}

Output:
Before concatenation:
string1 = first
string2 = second
After concatenation:
finalstr = firstsecond
string1 = firstsecond
string2 = second

Explanation:
string2 is appended at the end of string1 and contents of string2 are unchanged. In strct() function, using a for loop, all the characters of string 'c2' are copied at the end of c1. return (c1) is equivalent to return &c1[0] and it returns the base address of 'c1'. 'finalstr' stores that address returned by the function strct().

Compare Two Strings


Write a C program to compare two strings without using strcmp() function.

strcmp() function compares two strings lexicographically. strcmp is declared in stdio.h
Case 1: when the strings are equal, it returns zero.
Case 2: when the strings are unequal, it returns the difference between ascii values of the characters that differ.
a) When string1 is greater than string2, it returns positive value.
b) When string1 is lesser than string2, it returns negative value.
Syntax:
int strcmp (const char *s1, const char *s2);

Program: to compare two strings.

#include<stdio.h>
#include<string.h>
int cmpstr(char s1[10], char s2[10]);
int main() 
{
char arr1[10] = "Nodalo";
char arr2[10] = "nodalo";
printf(" %d", cmpstr(arr1, arr2));

// cmpstr() is equivalent of strcmp()

return 0;
}

// s1, s2 are strings to be compared

int cmpstr(char s1[10], char s2[10]) 
{
// strlen function returns the length of argument string passed
int i = strlen(s1);
int k = strlen(s2);
int bigger;
if (i < k) 
{
bigger = k;
}
else if (i > k) {
bigger = i;
}
else {
bigger = i;
}
// loops 'bigger' times
for (i = 0; i < bigger; i++) 
{
// if ascii values of characters s1[i], s2[i] are equal do nothing
if (s1[i] == s2[i]) 
{
}
//else return the ascii difference
else 
{
return (s1[i] - s2[i]);
}
}
//return 0 when both strings are same
//This statement is executed only when both strings are equal
return (0);
}

Output:
-32
Explanation:
cmpstr() is a function that illustrates C standard function strcmp(). Strings to be compared are sent as arguments to cmpstr(). Each character in string1 is compared to its corresponding character in string2. Once the loop encounters a differing character in the strings, it would return the ascii difference of the differing characters and exit.

Hello World


Write a C program to print "Hello World" without using semicolon anywhere in the code.

Generally when we use printf("") statement, we have to use a semicolon at the end. If printf is used inside an if
condition, semicolon can be avoided.

Program: Program to print some thing with out using semicolon(;)

#include <stdio.h>
int main() 
{

// printf returns the length of string being printed

if (printf("Hello World\n"))               //  prints Hello World and returns 11
{
//do nothing
}
return 0;
}

Output:
Hello World

Explanation:
The if statement checks for condition whether the return value of printf("Hello World") is greater than 0. printf function returns the length of the string printed. Hence the statement if (printf("Hello World")) prints the string "Hello World".

Fibonacci Series


Write a C program to generate the Fibonacci series.

Fibonacci series: Any number in the series is obtained by adding the previous two numbers of the series.
Let f(n) be n'th term.
f(0)=0;
f(1)=1;
f(n)=f(n-1)+f(n-2); (for n>=2)
Series is as follows
011
(1+0)
2 (1+1)
3 (1+2)
5 (2+3)
8 (3+5)
13 (5+8)
21 (8+13)
34 (13+21)
...and so on

Program: to generate Fibonacci Series(10 terms)

#include<stdio.h>
int main() 
{

int i, fib[25];                           //array fib stores numbers of Fibonacci series

fib[0] = 0;                              //initialized first element to 0

fib[1] = 1;                              //initialized second element to 1
for (i = 2; i < 10; i++)                //loop to generate ten elements
{

//i'th element of series is equal to the sum of i-1'th element and i-2'th element.

fib[i] = fib[i - 1] + fib[i - 2];

}
printf("The fibonacci series is as follows \n");

for (i = 0; i < 10; i++)                   //print all numbers in the series
{
printf("%d \n", fib[i]);
}
return 0;
}


Output:
The fibonacci series is as follows
01 1 2 3 5 8 13 21 34

Explanation:
The first two elements are initialized to 0, 1 respectively. Other elements in the series are generated by looping and adding previous two numbes. These numbers are stored in an array and ten elements of the series are printed as output.

Sunday, December 2

Program to Check Given String is a Palindrome


Write a C program to check whether the given string is a palindrome.

Palindrome is a string, which when read in both forward and backward way is same.
Example: radar, madam, pop, lol, Malayalam etc.,

Program:

#include <stdio.h>
#include <string.h>
int main() 
{
char string1[20];
int i, length;
int flag = 0;
printf("Enter a string: \n");
scanf("%s", string1);
length = strlen(string1);
for(i=0;i < length ;i++)
   {
       if(string1[i] != string1[length-i-1])
   {
       flag = 1;
       break;
    }
    }
if (flag) 
{
       printf("%s is not a palindrome\n", string1);
 }
else 
{
      printf("%s is a palindrome\n", string1);
 }
return 0;
}


Output:
Enter a string: radar
"radar" is a palindrome

Explanation with example:
To check if a string is a palindrome or not, a string needs to be compared with the reverse of itself.
Consider a palindrome string: "radar",
---------------------------
index: 0 1 2 3 4
value: r a d a r
---------------------------
To compare it with the reverse of itself, the following logic is used:
0th character in the char array, string1 is same as 4th character in the same string.
1st character is same as 3rd character.
2nd character is same as 2nd character.
. . . .
ith character is same as 'length-i-1'th character.
If any one of the above condition fails, flag is set to true(1), which implies that the string is not a palindrome.
By default, the value of flag is false(0). Hence, if all the conditions are satisfied, the string is a palindrome.

Palindromic Number



Write a C program to check whether the given number is a palindromic number.

If a number, which when read in both forward and backward way is same, then such a number is called a
palindrome number.

Program:

#include <stdio.h>
int main()
{
int n, n1, rev = 0, rem;
printf("Enter any number: \n");
scanf("%d", &n);
n1 = n;
/* logic */
while (n > 0)
    {
       rem = n % 10;
       rev = rev * 10 + rem;
       n = n / 10;
     }
if (n1 == rev)
    {
        printf("Given number is a palindromic number");
     }
else
    {
        printf("Given number is not a palindromic number");
     }
return 0;
}


Output:
Enter any number: 121
Given number is a palindrome

Explanation with an example:
Consider a number n=121, reverse=0, remainder;
number=121
now the while loop is executed /* the condition (n>0) is satisfied */
/* calculate remainder */
remainder of 121 divided by 10=(121%10)=1;
now reverse=(reverse*10)+remainder
=(0*10)+1 /* we have initialized reverse=0 */
=1
number=number/10
=121/10
=12
now the number is 12, greater than 0. The above process is repeated for number=12.
remainder=12%10=2;
reverse=(1*10)+2=12;
number=12/10=1;
now the number is 1, greater than 0. The above process is repeated for number=1.
remainder=1%10=1;
reverse=(12*10)+1=121;
number=1/10 /* the condition n>0 is not satisfied,control leaves the while loop */
Program stops here. The given number=121 equals the reverse of the number. Thus the given number is a
palindrome number.

Program to Check Whether The Given Number is a Prime



Write a C program to check whether the given number is a prime

A prime number is a natural number that has only one and itself as factors. Examples: 2, 3, 13 are prime numbers.

Program:

#include <stdio.h>
main()
{
int n, i, c = 0;
printf("Enter any number n: \n");
scanf("%d", &n);
/*logic*/
for (i = 1; i <= n; i++)
   {
         if (n % i == 0)
              {
                  c++;
               }
    }
if (c == 2) 
   {
       printf("n is a Prime number");
    }
else 
    {
       printf("n is not a Prime number");
     }
return 0;
}


Output:
Enter any number n: 7
n is Prime
Explanation with examples:
consider a number n=5
for(i=0;i<=n;i++) /* for loop is executed until the n value equals i */
i.e. for(i=0;i<=5;i++) /* here the for loop is executed until i is equal to n */
1st iteration: i=1;i<=5;i++
here i is incremented i.e. i value for next iteration is 2
now if(n%i==0) then c is incremented
i.e.if(5%1==0)then c is incremented, here 5%1=0 thus c is incremented.
now c=1;
2nd iteration: i=2;i<=5;i++
here i is incremented i.e. i value for next iteration is 3
now if(n%i==0) then c is incremented
i.e.if(5%2==0) then c is incremented, but 5%2!=0 and so c is not incremented, c remains 1
c=1;
3rd iteration: i=3;i<=5;i++
here i is incremented i.e. i value for next iteration is 4
now if(n%i==0) then c is incremented
i.e.if(5%3==0) then c ic incremented, but 5%3!=0 and so c is not incremented, c remains 1
c=1;
4th iteration: i=4;i<=5;i++
here i is incremented i.e. i value for next iteration is 5
now if(n%i==0) then c is incremented
i.e. if(5%4==0) then c is incremented, but 5%4!=0 and so c is not incremented, c remains 1
c=1;
5th iteration: i=5;i<=5;i++
here i is incremented i.e. i value for next iteration is 6
now if(n%i==0) then c is incremented
i.e. if(5%5==0) then c is incremented, 5%5=0 and so c is incremented.
i.e. c=2
6th iteration: i=6;i<=5;i++
here i value is 6 and 6<=5 is false thus the condition fails and control leaves the for loop.
now if(c==2) then n is a prime number
we have c=2 from the 5th iteration and thus n=5 is a Prime number.

Friday, November 30

Program To Find The Greatest Among Ten Numbers



Write a C program to find the greatest among ten numbers.

Program:

#include <stdio.h>
int main() 
{
int a[10];
int i;
int greatest;
printf("Enter ten values:");


for (i = 0; i < 10; i++)                                         //Store 10 numbers in an array
   {
      scanf("%d", &a[i]);
    }


greatest = a[0];                                                  //Assume that a[0] is greatest
for (i = 0; i < 10; i++) 
  {
if (a[i] > greatest) 
      {
           greatest = a[i];
       }
  }
printf("\nGreatest of ten numbers is %d", greatest);
return 0;
}


Output:
Enter ten values: 2  53  65  3  88  8  14  5  77  64 Greatest of ten numbers is 88

Explanation with example:
Entered values are 2, 53, 65, 3, 88, 8, 14, 5, 77, 64
They are stored in an array of size 10. let a[] be an array holding these values.
/* how the greatest among ten numbers is found */
Let us consider a variable 'greatest'. At the beginning of the loop, variable 'greatest' is assinged with the value of
first element in the array greatest=a[0]. Here variable 'greatest' is assigned 2 as a[0]=2.
Below loop is executed until end of the array 'a[]';.
for(i=0; i<10; i++)
{
if(a[i]>greatest)
{
greatest= a[i];
}
}
For each value of 'i', value of a[i] is compared with value of variable 'greatest'. If any value greater than the value
of 'greatest' is encountered, it would be replaced by a[i]. After completion of 'for' loop, the value of variable
'greatest' holds the greatest number in the array. In this case 88 is the greatest of all the numbers