DEV Community: Punitha

Tableau SetUp

Punitha — Fri, 14 Aug 2026 02:59:02 +0000

Step 1: Visit the Tableau Website

Open your web browser
Go to the official Tableau website
Navigate to the Products section

Step 2: Download Tableau Public

Click Download Tableau Public
Choose the version compatible with your OS
Wait for the download to complete

Step 3: Run the Installer

Open the downloaded installation file
If prompted, allow the installer to make changes to your computer

Step 4: Accept the License Agreement

Read the license agreement
Select I accept the terms
Click Install

Step 5: Wait for Installation

Tableau will install the required files
This may take a few minutes

Step 6: Launch Tableau

After installation is complete, click Finish
Open Tableau Public from the Start Menu or Desktop shortcut

Step 7: Sign In or Create Account

Sign in using your Tableau account
If you don't have an account, create a free Tableau Public account

Step 8: Verify the Installation

Once Tableau opens successfully, you will see the Start Page
The installation is now complete

SQL Procedure

Punitha — Thu, 13 Aug 2026 03:12:23 +0000

What is a Procedure?

A Procedure is a collection of SQL statements stored in the database. It performs one or more database operations whenever it is executed.

Why Do We Need a Stored Procedure?

Suppose every day you need to:

Insert new students
Update marks
Display reports

Instead of writing many SQL statements every day, you can save them in one stored procedure and execute it whenever needed.

How Does a Procedure Work?

User
  |
CALL Procedure
  |
Stored Procedure
  |
Runs Multiple SQL Statements
  |
Returns Result

Syntax (PostgreSQL)

CREATE PROCEDURE procedure_name()
LANGUAGE SQL
AS $$
SQL Statements;
$$;

Example

CREATE PROCEDURE ShowStudents()
LANGUAGE SQL
AS $$
SELECT * FROM Student;
$$;

Execute

CALL ShowStudents();

Why Use a Procedure?

Execute multiple SQL statements together
Reduce repeated SQL code
Improve performance
Increase security
Automate database tasks

Advantages

Saves SQL code
Faster execution
Reusable
Easy to maintain
Improves security

SQL Functions

Punitha — Wed, 12 Aug 2026 02:12:13 +0000

What is a Function?

A Function is a database object that performs a specific tack. It accepts input values, processes them, and returns a single value or a table.

Why Do We Need a Function?

Suppose you want to calculate the Total Price many times.

Instead of writing:

SELECT Quantity * Price
FROM Product;

again and again, you can create a Function once and reuse it.

How Does a Function Work?

Input
  |
Function
  |
Process
  |
Output

Syntax: (PostgreSQL)

CREATE FUNCTION function_name(parameters)
RETURNS datatype
LANGUAGE SQL
AS $$
    SQL Query
$$;

Example:

CREATE FUNCTION AddNumbers(a INT, b INT)
RETURNS INT
LANGUAGE SQL
AS $$
    SELECT a + b;
$$;

Execute

SELECT AddNumbers(10,20);

Output:

Why Use a Function?

Perform calculations
Reuse SQL code
Reduce repeated queries
Improve readability
Return a value automatically

Advantage

Reusable
Easy to maintain
Reduces coding
Faster execution
Returns a result

SQL Views

Punitha — Tue, 11 Aug 2026 03:05:08 +0000

What is a View?

A View is a virtual table created from one or more existing tables using an SQL query.
It does not store data separately.
Instead, it displays data from the original table whenever it is queried.

Why Use a View?

Simplify complex SQL queries
Show only the required columns
Hide sensitive information (salary or password)
Improve security
Make reports easier to create

How Does a View Work?

Student Table
     |
CREATE VIEW
     |
Student_View
     |
SELECT * FROM Student_View;

Syntax:

Create View

CREATE VIEW Student_View AS
SELECT Student_ID, Name, Marks
FROM Student;

Retrieve Data

SELECT * FROM Student_View;

Advantages of Views:

Easy to use
Improves security
Makes reports simple
Reuses SQL queries

SQL Joins

Punitha — Mon, 10 Aug 2026 02:15:28 +0000

What are SQL Joins?

SQL Joins are used to combine data from two or more tables based on a related column.

Why are Joins Used?

Combine data from multiple tables
Reduce duplicate data
Retrieve related information
Generate meaningful reports

Types of Joins:

INNER JOIN
LEFT JOIN
RIGHT JOIN
FULL JOIN
SELF JOIN
CROSS JOIN

INNER JOIN

The INNER JOIN returns only the records that have matching values in both tables.

Syntax:

SELECT columns
FROM table1
INNER JOIN table2
ON table 1.column = table2.column

Example:

SELECT Student.Name,
Department.Department
FROM Student
INNER JOIN Department
ON Student.Dept_ID = Department.Dept_ID;

LEFT JOIN

The LEFT JOIN returns all records from the left table and the matching records from the right table. If there is no match, NULL values are returned.

Syntax:

SELECT columns
FROM table1
LEFT JOIN table2
ON table1.column = table2.column;

Example:

SELECT Student.Name,
Department.Department
FROM Student
LEFT JOIN Department
ON Student.Dept_ID = Department.Dept_ID;

RIGHT JOIN

The RIGHT JOIN returns all records from the right table and the matching records from the left table. If there is no match, NULL values are returned.

Syntax:

SELECT columns
FROM table1
RIGHT JOIN table2
ON table1.column = table2.column;

Example:

SELECT Student.Name,
Department.Department
FROM Student
RIGHT JOIN Department
ON Student.Dept_ID = Department.Dept_ID;

FULL JOIN

The FULL JOIN returns all records from both tables. If there is no match, NULL values are displayed.

Syntax:

SELECT Student.Name,
Department.Department
FROM Student
INNER JOIN Department
ON Student.Dept_ID = Department.Dept_ID;

Example:

SELECT Student.Name,
Department.Department
FROM Student
FULL JOIN Department
ON Student.Dept_ID = Department.Dept_ID;

SELF JOIN

A SELF JOIN joins a table with itself.

Example:

SELECT
A.Employee AS Employee,
B.Employee AS Manager
FROM Employee A
INNER JOIN Employee B
ON A.Manager_ID = B.Employee_ID;

CROSS JOIN

The CROSS JOIN returns every possible combination of rows from two tables.

Syntax:

SELECT columns
FROM table1
CROSS JOIN table2;

Example:

SELECT Student.Name,
Department.Department
FROM Student
CROSS JOIN Department;

SQL Constraints

Punitha — Sat, 08 Aug 2026 02:35:41 +0000

What are SQL Constraints?

SQL Constraints are rules applied to table columns to ensure that the data stored in the database is accurate, valid, and consistent.

Why are Constraints Used?

Ensure data accuracy
Prevent invalid data
Avoid duplicate records
Maintain relationships between tables
Improve data integrity

Types of SQL Constraints

PRIMARY KEY
FOREIGN KEY
NOT NULL
UNIQUE
CHECK
DEFAULT

PRIMARY KEY

A PRIMARY KEY uniquely identifies each record in a table.
Values must be unique
Cannot contain NULL values
A table can have only one primary key

CREATE TABLE Student(
       Student_ID INT PRIMARY KEY,
       Name VARCHAR(50),
       Marks INT
);

FOREIGN KEY

A FOREIGN KEY creates a relationship between two tables by referring to the primary key of another table.

Department Table

CREATE TABLE Department(
      Dept_ID INT PRIMARY KEY,
      Department_Name VARCHAR(50)
);

Student Table

CREATE TABLE Student(
      Student_ID INT PRIMARY KEY,
      Name VARCHAR(50),
      Dept_ID INT,
      FOREIGN KEY (Dept_ID) REFERENCES Department(Dept_ID)
);

NOT NULL

The NOT NULL constraint ensures that a column cannot contain NULL(empty) values.

CREATE TABLE Student(
      Student_ID INT,
      Name VARCHAR(50) NOT NULL
);

UNIQUE

The UNIQUE constraint ensures that all values in a column are different.

CREATE TABLE Student(
      Student_ID INT PRIMARY KEY,
      Email VARCHAR(100) UNIQUE
);

CHECK

The CHECK constraint ensures that values meet a specified condition.

CREATE TABLE Student(
      Student_ID INT,
      Marks INT CHECK (Marks >= 0 AND Marks <= 100)
);

DEFAULT

The DEFAULT constraint assigns a default value if no value is provided.

CREATE TABLE Student(
       Student_ID INT,
       City VARCHAR(50) DEFAULT 'Chennai'
);

SQL Functions

Punitha — Fri, 07 Aug 2026 03:23:37 +0000

What are SQL Functions?

SQL functions perform calculations on data and return a result.

COUNT()
SUM()
AVG()
MIN()
MAX()

COUNT()

Returns the total number of rows.

SELECT COUNT(*)
FROM Employee;

SUM()

Returns total value of a numeric column.

SELECT SUM(Salary)
FROM Employee;

AVG()

Returns the average value.

SELECT AVG(Salary)
FROM Employee;

MIN()

Returns the smallest value.

SELECT MIN(Salary)
FROM Employee;

MAX()

Returns the largest value.

SELECT MAX(Salary)
FROM Employee;

SQL Clauses

Punitha — Thu, 06 Aug 2026 02:12:08 +0000

What are SQL Clauses?

SQL clauses are used to filter, sort, group, and organize query results.

WHERE
ORDER BY
GROUP BY
HAVING

WHERE Clause

The WHERE clause filters records based on a condition.

SELECT *
FROM Employee
WHERE Salary > 50000;

ORDER BY Clause

The ORDER BY clause sorts the result in ascending or descending order.

SELECT *
FROM Employee
ORDER BY Salary DESC;

GROUP BY Clause

The GROUP BY clause groups rows that have the same values.

SELECT Department, COUNT(*)
FROM Employee
GROUP BY Department;

HAVING Clause

The HAVING clause filters grouped data.

SELECT Department, COUNT(*)
FROM Employee
GROUP BY Department
HAVING COUNT(*) > 5;

SQL Operators

Punitha — Wed, 05 Aug 2026 01:49:37 +0000

What are SQL Operators?

SQL Operators are symbols or keywords used to perform operations on data and compare values in SQL queries.

Arithmetic Operators

Arithmetic operators are used to perform mathematical calculations.

Operator     Description

  +           Addition
  -           Substraction
  *           Multiplication
  /           Division
  %           Modulus

Comparison Operators

Comparison operators compare two values.

Operator        Description

   =             Equal to
   >             Greater than
   <             Less than
   >=            Greater than or equal to
   <=            Less than or equal to
   <> or !=      Not equal to

Logical Operators

Logical operators combine multiple conditions.

Operator    Description

  AND       Both conditions must be true
  OR        At least one condition must be true
  NOT       Reverses the condition

IN Operator

The IN operator checks whether a value matches any value in a list.

SELECT *
FROM table_name
WHERE column_table IN (value1, value2);

SELECT *
FROM Employee
WHERE Department IN ('IT','HR')

BETWEEN Operator

The BETWEEN operator selects value within a range.

SELECT *
FROM Employee
WHERE Salary BETWEEN 30000 AND 60000;

LIKE Operator

The LIKE operator searches for a specific pattern in text.

SELECT *
FROM Employee
WHERE Name LIKE 'p%';

IS NULL Operator

The IS NULL operator checks for empty (NULL) values.

SELECT *
FROM Employee
WHERE Email IS NULL;

DML & DQL

Punitha — Tue, 04 Aug 2026 02:04:43 +0000

What is DML?

DML (Data Manipulation Language) is used to insert, update, and delete data stored in database tables.

INSERT
UPDATE
DELETE

INSERT - The INSERT statement adds new records to a table.

INSERT INTO table_name(column1, column2)
VALUES (value1, value2);

INSERT INTO Student
VALUES (101, 'John', 90);

UPDATE - The UPDATE statement modifies existing records.

UPDATE table_name
SET column_name = value
WHERE condition;

UPDATE Student
SET Marks = 95
WHERE Student_ID = 101;

DELETE - The DELETE statements removes records from a table.

DELETE FROM table_name
WHERE condition;

DELETE FROM Student
WHERE Student_ID = 101;

What is DQL?

DQL (Data Query Language) is used to retrieve data from a database.

SELECT

SELECT - The SELECT statement retrieves one or more records from a table.

SELECT column_name
FROM table_name;

SELECT * FROM Student;

SELECT Name FROM Student;

DDL (Data Definition Language)

Punitha — Mon, 03 Aug 2026 04:17:38 +0000

What is DDL?
DDL is used to create, modify, and delete database objects such as databases, tables, and schemas.

CREATE
ALTER
DROP
TRUNCATE
RENAME

CREATE - The CREATE statement is used to create a new database or a new table.

CREATE TABLE table_name(
       column1 datatype,
       column2 datatype
);

CREATE TABLE Student(
      Student_ID INT,
      Name VARCHAR(50),
      Marks INT
);

ALTER - The ALTER statement is used to modify the structure of an existing table.

ALTER TABLE table_name
ADD column_name datatype;

ALTER TABLE Student
ADD Department VARCHAR(50);

DROP - The DROP statement is used to permanently delete a database or table.

DROP TABLE table_name;

DROP TABLE Student;

TRUNCATE - The TRUNCATE statement removes all records from a table but keeps the table structure.

TRUNCATE TABLE table_name;

TRUNCATE TABLE Student;

RENAME - The RENAME statement changes the name of a table.

ALTER TABLE old_table_name
RENAME TO new_table_name;

ALTER TABLE Student
RENAME TO Student_Details;

CRUD Operations in SQL

Punitha — Fri, 31 Jul 2026 12:41:59 +0000

CRUD stands for Create, Read, Update, and Delete.
These are the four basic operations used to manage data in a database.
SQL provides different commands to perform each of these operations.

CRUD stands for:

C -> Create
R -> Read
U -> Update
D -> Delete

Definition:

Create(INSERT) - The INSERT statement is used to add new records into a table.

INSERT INTO table_name(col1,col2,.....)
VALUES (value1,value2,.....);

INSERT INTO Student (Student_ID, Name, Marks)
VALUES (101, 'John', 90);

Read(SELECT) - The SELECT statement is used to retrieve data from a table.

SELECT column_name
FROM table_name;

SELECT * FROM Student;

Update - The UPDATE statement is used to modify existing records in a table

UPDATE table_name
SET column_name = value
WHERE condition;

UPDATE Student
SET Marks = 95
WHERE Student_ID = 101;

Delete - The DELETE statement is used to remove records from a table

DELETE FROM Student
WHERE Student_ID = 101;

DELETE FROM Student
WHERE Student_ID = 101;