DEV Community: Annapoorani Kadhiravan

One Commit at a Time ! Series - 28

Annapoorani Kadhiravan — Mon, 02 Nov 2026 18:21:40 +0000

C Sharp

SQL

References :

One Commit at a Time ! Series - 27

Annapoorani Kadhiravan — Sun, 01 Nov 2026 17:55:32 +0000

DOT NET

What is C#?
C# is pronounced "C-Sharp".

It is an object-oriented programming language created by Microsoft that runs on the .NET Framework.

C# has roots from the C family, and the language is close to other popular languages like C++ and Java.

The first version was released in year 2002. The latest version, C# 14, was released in November 2025.

C# is used for:

Mobile applications
Desktop applications
Web applications
Web services
Web sites
Games
VR
Database applications

Why Use C#?
It is one of the most popular programming languages in the world
It is easy to learn and simple to use
It has huge community support
C# is an object-oriented language which gives a clear structure to programs and allows code to be reused, lowering development costs
As C# is close to C, C++ and Java, it makes it easy for programmers to switch to C# or vice versa

SQL

Combining AND and OR
You can also combine AND and OR operators.

The following SQL selects all customers from Spain that starts with a "G" or an "R" (make sure to use parenthesis to get the correct result):

Example
Select all Spanish customers that starts with either "G" or "R":

SELECT * FROM Customers
WHERE Country = 'Spain' AND (CustomerName LIKE 'G%' OR CustomerName LIKE 'R%');

References
https://www.w3schools.com/sql/sql_and.asp
https://www.w3schools.com/cs/cs_intro.php

One Commit at a Time ! Series - 26

Annapoorani Kadhiravan — Sat, 31 Oct 2026 17:33:28 +0000

JAVA

public class Main {
  public static void main(String[] args) {
    int x = 5;
    System.out.println(x > 3 && x < 10); // returns true because 5 is greater than 3 AND 5 is less than 10
  }
}

Explanation :

int x = 5;
Declares an integer variable named x and assigns it the value 5.
x > 3
Evaluates whether x (which is 5) is greater than 3. This statement is true.
x < 10
Evaluates whether x (which is 5) is less than 10. This statement is true.
x > 3 && x < 10
The && symbol is the logical AND operator. It requires both sides of the expression to be true for the entire condition to be true.
Since 5 > 3 is true and 5 < 10 is true, the overall result of the expression is true.
System.out.println(...)
Prints the result of the expression (true) to the console.

SQL

All Conditions Must Be True
The following SQL selects all customers where Country is "Brazil" AND City is "Rio de Janeiro" AND CustomerID is higher than 50:

Example

SELECT * FROM Customers
WHERE Country = 'Brazil'
AND City = 'Rio de Janeiro'
AND CustomerID > 50;

References:
https://www.w3schools.com/sql/sql_and.asp
https://www.w3schools.com/java/java_examples.asp

One Commit at a Time ! Series - 25

Annapoorani Kadhiravan — Fri, 30 Oct 2026 16:36:36 +0000

JAVA

public class Main {
  public static void main(String[] args) {
    int x = 5;
    System.out.println(x);
  }
}

Explanation :

1. The Class Definition

public class Main {

public class Main: In Java, every program must be enclosed in a class. This defines a public class named Main. By convention, the name of the main class usually matches the filename (Main.java).

2. The Main Method

  public static void main(String[] args) {

public static void main(String[] args): This is the entry point of any standalone Java application. The Java runtime always looks for this exact method signature to start running the program.
public: Means this method can be accessed from outside the class.
static: Means the method belongs to the class itself, rather than an instance of the class, so Java can call it without creating an object.
void: Means this method does not return any value.
String[] args: This is an array that can store command-line arguments passed to the program.

3. Variable Declaration and Assignment

    int x = 5;

int x = 5;: This declares a variable named x of type int (integer, meaning whole numbers) and assigns it the value 5.

4. Printing to the Console

    System.out.println(x);

System.out.println(x);: This tells Java to print the value stored in the variable x to the console, followed by a new line.

Output

When you run this program, the console will display:

SQL

The WHERE clause can contain one or many AND operators.

The AND operator is used to filter records based on more than one condition.

Note: The AND operator displays a record if all the conditions are TRUE.

The following SQL selects all customers from Spain that starts with the letter 'G':

Example

Select all customers where Country is "Spain" AND CustomerName starts with the letter 'G':
SELECT *
FROM Customers
WHERE Country = 'Spain' AND CustomerName LIKE 'G%';

References :
https://www.w3schools.com/sql/sql_and.asp
https://www.w3schools.com/java/tryjava.asp?filename=demo_oper_ass1

One Commit at a Time ! Series - 24

Annapoorani Kadhiravan — Thu, 29 Oct 2026 16:28:03 +0000

JAVA

public class Main {
  public static void main(String[] args) {
    int x = 5;
    --x;
    System.out.println(x);
  }
}

Explanation :

This Java program demonstrates the use of the decrement operator (--) to decrease the value of a variable.

Here is a step-by-step breakdown:

int x = 5;
Declares an integer variable named x and initializes it with the value 5.
--x;
Applies the pre-decrement operator to x. This subtracts 1 directly from the current value of x.
Since x was 5, it now becomes 4. (Because it is placed before the variable, it decrements the value immediately).
System.out.println(x);
Prints the current value of x (4) to the console.

Output

SQL

SELECT Example Without DISTINCT
If you omit the DISTINCT keyword, the SQL statement returns the "Country" value from all the records of the "Customers" table:

Example

SELECT Country FROM Customers;

References :

https://www.w3schools.com/sql/sql_distinct.asp
https://www.w3schools.com/java/java_examples.asp

One Commit at a Time ! Series - 23

Annapoorani Kadhiravan — Wed, 28 Oct 2026 18:21:11 +0000

JAVA

public class Main {
  public static void main(String[] args) {
    int x = 5;
    ++x;
    System.out.println(x);
  }
}

Explanation :

This Java program demonstrates the use of the increment operator (++) to increase the value of a variable.

Here is a step-by-step breakdown:

int x = 5;
Declares an integer variable named x and initializes it with the value 5.
++x;
Applies the pre-increment operator to x. This adds 1 directly to the current value of x.
Since x was 5, it now becomes 6. (Because it is placed before the variable, it increments the value immediately before using it).
System.out.println(x);
Prints the current value of x (6) to the console.

Output

SQL

SQL SELECT DISTINCT Statement
The SELECT DISTINCT statement is used to return only distinct (unique) values.

In a table, a column may contain several duplicate values - and sometimes you want to list only the unique values.

Example
Select all the distinct (unique) countries from the "Customers" table:

SELECT DISTINCT Country FROM Customers;

SELECT DISTINCT Syntax

SELECT DISTINCT column1, column2, ...
FROM table_name;

References :

https://www.w3schools.com/sql/sql_distinct.asp
https://www.w3schools.com/java/java_examples.asp

One Commit at a Time ! Series - 22

Annapoorani Kadhiravan — Tue, 27 Oct 2026 17:19:30 +0000

JAVA

public class Main {
  public static void main(String[] args) {
    int x = 5;
    int y = 3;
    System.out.println(x + y);
  }
}

Explanation :

This Java program is a simple script that performs basic arithmetic by adding two integers and printing the result.

Here is a step-by-step breakdown:

int x = 5;
Declares an integer variable named x and initializes it with the value 5.
int y = 3;
Declares an integer variable named y and initializes it with the value 3.
System.out.println(x + y);
Adds the values of x and y together ($5 + 3$) and prints the resulting sum (8) to the console.

Output

SQL

Operators in The WHERE Clause
You can use other operators than the = operator to filter the search.

Example
Select all customers with a CustomerID greater than 80:

SELECT * FROM Customers
WHERE CustomerID > 80;

References :
https://www.w3schools.com/sql/sql_where.asp
https://www.w3schools.com/java/java_examples.asp

One Commit at a Time ! Series - 21

Annapoorani Kadhiravan — Mon, 26 Oct 2026 16:57:28 +0000

JAVA

public class Main {
  public static void main(String[] args) {
    double myDouble = 9.78d;
    int myInt = (int) myDouble; // Explicit casting: double to int

    System.out.println(myDouble);
    System.out.println(myInt);
  }
}

Explanation :

This Java program demonstrates type casting, specifically converting a double (a floating-point decimal number) into an int (a whole number) using explicit casting.

Here is a step-by-step breakdown:

double myDouble = 9.78d;
Declares a variable named myDouble of type double and assigns it the value 9.78. The d suffix explicitly denotes a double literal (though it is optional in Java).
int myInt = (int) myDouble;
Performs explicit casting (also known as narrowing conversion). Because a double can hold decimals and an int cannot, Java requires you to explicitly tell it to convert the type by putting (int) in front of the variable.
Crucial detail: When casting a floating-point number to an integer, Java truncates the decimal part entirely—it does not round up. Therefore, 9.78 becomes 9.
System.out.println(myDouble);
Prints the original double value to the console: 9.78.
System.out.println(myInt);
Prints the converted integer value to the console: 9.

Output

9.78
9

SQL

Text Fields vs. Numeric Fields
SQL requires single quotes around text values (most database systems will also allow double quotes).

However, numeric fields should not be enclosed in quotes:

Example

SELECT * FROM Customers
WHERE CustomerID = 1;

References

https://www.w3schools.com/sql/sql_where.asp
https://www.w3schools.com/java/java_examples.asp

One Commit at a Time ! Series - 20

Annapoorani Kadhiravan — Sun, 25 Oct 2026 13:31:44 +0000

JAVA

public class Main {
  public static void main(String[] args) {
    int myInt = 9;
    double myDouble = myInt; // Automatic casting: int to double

    System.out.println(myInt);
    System.out.println(myDouble);
  }
}

Explanation :

This program demonstrates widening casting (also known as implicit casting or type promotion) in Java, where a smaller primitive data type is automatically converted into a larger primitive data type.

Step-by-step breakdown:

int myInt = 9;: Declares an integer variable named myInt and assigns it the value 9.
double myDouble = myInt;: Automatically casts the integer value to a double. Because a double has a larger memory footprint and can hold decimals, Java performs this conversion safely behind the scenes without any data loss.
System.out.println(myInt);: Prints the integer value (9) to the console.
System.out.println(myDouble);: Prints the converted double value (9.0) to the console.

The output of the program will be:

9
9.0

Widening Casting in Detail

Widening casting happens when you assign a value of a smaller data type to a variable of a larger data type. In Java, this process is automatic (implicit) because there is no risk of losing magnitude or precision during the conversion.

The Java Primitive Type Hierarchy

To understand why casting is necessary or automatic, look at the size hierarchy of Java's numeric primitive types (from smallest to largest):

$$\text{byte} \rightarrow \text{short} \rightarrow \text{int} \rightarrow \text{long} \rightarrow \text{float} \rightarrow \text{double}$$

(Note: char behaves like a 16-bit unsigned integer and can also be widened to int or larger types).

Key Characteristics of Widening Casting

Safe Conversion: Since the target type has an equal or greater capacity than the source type, the original value fits completely within the new memory allocation.
No Explicit Syntax Required: Unlike narrowing casting (which requires manual casting syntax like (int) myDouble), widening happens implicitly. You do not need to write type cast operators.
Precision Preservation: Converting integers to floating-point numbers (int to double or float) preserves whole numbers while adding a decimal representation (e.g., 9 becomes 9.0). However, casting very large long values to float or double can occasionally result in a minor loss of fractional precision because of how floating-point numbers are stored in memory, though the magnitude remains accurate.

SQL

Operators in The WHERE Clause
You can use other operators than the = operator to filter the search.

Example
Select all customers with a CustomerID greater than 80:

SELECT * FROM Customers
WHERE CustomerID > 80;

References :
https://www.w3schools.com/sql/sql_where.asp
https://www.w3schools.com/java/java_examples.asp

One Commit at a Time ! Series - 19

Annapoorani Kadhiravan — Sat, 24 Oct 2026 16:49:47 +0000

JAVA

public class Main {
  public static void main(String[] args) {
    String x = "10";
    int y = 20;
    String z = x + y;
    System.out.println(z);
  }
}

Explanation :

This program demonstrates string concatenation and type coercion in Java. When a String is added to a primitive data type like an int using the + operator, Java automatically converts the integer into a string and concatenates them together rather than performing mathematical addition.

Step-by-step breakdown:

String x = "10";: Declares a string variable named x holding the text "10".
int y = 20;: Declares an integer variable named y holding the numeric value 20.
String z = x + y;: Combines x and y. Because x is a String, the integer y is converted to the string "20" and joined with "10", resulting in the string "1020".
System.out.println(z);: Prints the final value of z to the console.

The output of the program will be:

SQL

Text Fields vs. Numeric Fields
SQL requires single quotes around text values (most database systems will also allow double quotes).

However, numeric fields should not be enclosed in quotes:

Example

SELECT * FROM Customers
WHERE CustomerID = 1;

References :
https://www.w3schools.com/sql/sql_where.asp
https://www.w3schools.com/java/java_examples.asp

One Commit at a Time ! Series - 18

Annapoorani Kadhiravan — Fri, 23 Oct 2026 16:37:59 +0000

JAVA

public class Main {
  public static void main(String[] args) {
    String txt = "Hello World";
    System.out.println(txt.toUpperCase());
    System.out.println(txt.toLowerCase());
  }
}

Explanation :

This Java program demonstrates how to transform the casing of characters in a string using built-in string methods.

public class Main: The container class required by Java to hold the executable code.
public static void main(String[] args): The main entry point where program execution begins.
String txt = "Hello World";: Creates a String variable named txt containing the characters "Hello World".
txt.toUpperCase(): Returns a new string with every letter converted to uppercase ("HELLO WORLD").
txt.toLowerCase(): Returns a new string with every letter converted to lowercase ("hello world").
System.out.println(...): Prints each converted string to the console on a new line, leaving the original txt variable unchanged since strings in Java are immutable.

SQL

WHERE Clause
The WHERE clause is used to filter records.

The WHERE clause is used to extract only those records that fulfill a specific condition.

Example
Here we select all customers from Mexico:

SELECT * FROM Customers
WHERE Country = 'Mexico';

References :
https://www.w3schools.com/sql/sql_where.asp
https://www.w3schools.com/java/java_examples.asp

One Commit at a Time ! Series - 17

Annapoorani Kadhiravan — Thu, 22 Oct 2026 18:08:48 +0000

JAVA

public class Main {
  public static void main(String[] args) {
    String txt = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
    System.out.println("The length of the txt string is: " + txt.length());
  }
}

Explanation :

This Java program calculates and prints the number of characters inside a given text string.

public class Main: Defines the main container class for the program, which Java requires for all code execution.
public static void main(String[] args): The entry point or starting mechanism where the Java Virtual Machine begins running the code.
String txt = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";: Declares a variable named txt of type String and assigns it the entire alphabet in uppercase letters.
txt.length(): Calls the built-in length() method on the string object, which counts every character stored inside txt.
System.out.println(...): Outputs the resulting string concatenation—combining the descriptive text with the number 26—directly to your console screen.

SQL

ORDER BY Several Columns
The following SQL statement selects all customers from the "Customers" table - and sorts it by the "Country" and the "CustomerName" column.

This means that it sorts it first by Country, and if some records have the same Country, it sorts them by CustomerName:

SELECT * FROM Customers
ORDER BY Country, CustomerName;

Combine ASC and DESC
The following SQL statement selects all customers from the "Customers" table, and sorts it ASCENDING by the "Country" and DESCENDING by the "CustomerName" column:

SELECT * FROM Customers
ORDER BY Country ASC, CustomerName DESC;

References :
https://www.w3schools.com/sql/sql_orderby.asp
https://www.w3schools.com/java/java_examples.asp