DEV Community: Guru prasanna

Oracle PL/SQL - Basic Terms

Guru prasanna — Fri, 16 May 2025 07:25:28 +0000

Term	Explanation
PL/SQL	Procedural Language extension of SQL used in Oracle databases. It adds procedural features like variables, loops, and conditions to SQL.
Block	The basic unit of a PL/SQL program. Every PL/SQL code is written in blocks (anonymous or named).
DECLARE	Section to declare variables, constants, cursors, and exceptions (optional).
BEGIN	Mandatory section where the actual executable code (SQL & PL/SQL statements) is written.
EXCEPTION	Optional section to handle runtime errors (exceptions).
END	Marks the end of the PL/SQL block.
Variable	A placeholder to store data temporarily during program execution.
Constant	A variable whose value cannot be changed once initialized.
Cursor	Used to retrieve multiple rows from a SELECT query, row-by-row.
Loop	Allows repeated execution of a block of code.
IF-THEN-ELSE	Conditional statement to perform different actions based on conditions.
Procedure	A named PL/SQL block that performs a task.
Function	Similar to a procedure, but it returns a value.
Trigger	A PL/SQL block that executes automatically in response to an event (e.g., insert, update).
Exception	Error condition during execution (e.g., NO_DATA_FOUND, TOO_MANY_ROWS).

Basic syntax:

DECLARE
   -- Variable declarations
   variable_name datatype;
BEGIN
   -- Executable statements
   -- SQL and PL/SQL code goes here
   DBMS_OUTPUT.PUT_LINE('Hello PL/SQL!');
EXCEPTION
   -- Exception handling
   WHEN OTHERS THEN
     DBMS_OUTPUT.PUT_LINE('An error occurred.');
END;
/

Javascript - ServiceNow

Guru prasanna — Mon, 28 Apr 2025 09:19:54 +0000

How is JavaScript linked with ServiceNow?

ServiceNow is built on JavaScript.
Almost all the backend scripts (like Business Rules, Script Includes, Scheduled Jobs) are written using Server-side JavaScript.
Client-side scripts (like Client Scripts, UI Policies, Catalog Client Scripts) also use JavaScript to control what happens on the user’s browser.
Glide API is ServiceNow’s built-in library written in JavaScript — it helps you easily interact with the ServiceNow database.

➔ In short: ServiceNow = JavaScript + ServiceNow's Glide API.

JavaScript Interview Questions (ServiceNow Focused)

1. How is JavaScript used in ServiceNow?

Answer:

JavaScript is used both on the client-side (browser) and server-side (server) in ServiceNow.

Client-side scripting is used for form manipulation, field validation, and UI actions (example: Client Script, Catalog Client Script).
Server-side scripting is used for database operations, automation, and backend processing (example: Business Rules, Script Includes).

2. What is a Client Script in ServiceNow?

Answer:

A Client Script is a piece of JavaScript that runs on the client’s browser when forms are loaded, changed, or submitted.

It is used to:

Auto-populate fields
Validate input before saving
Display alerts or messages

Example:

function onLoad() {
  alert('Welcome to the form!');
}

3. What is a Business Rule in ServiceNow?

Answer:

A Business Rule is a server-side script that runs when records are inserted, updated, deleted, or queried.

It is used to:

Automate tasks
Enforce business logic
Interact with the database

Example:

(function executeRule(current, gsn, gs) {
  current.short_description = 'Updated by Business Rule';
})(current, gsn, gs);

4. What is GlideRecord in ServiceNow?

Answer:

GlideRecord is a JavaScript class used to query, read, update, and delete records in ServiceNow tables (server-side).

Example:

var gr = new GlideRecord('incident');
gr.addQuery('priority', 1);
gr.query();
while (gr.next()) {
  gs.info(gr.number);
}

5. Difference between Client-side and Server-side scripting in ServiceNow?

Feature     | Client-side        | Server-side
Runs where? | User's browser     | ServiceNow server
Example     | Client Script      | Business Rule
Purpose     | Form behavior      | Database operations
API used    | GlideForm (g_form) | GlideRecord (gr), GlideSystem (gs)

6. What is a Script Include in ServiceNow?

Answer:

A Script Include is a reusable server-side JavaScript function or library that you can call from other scripts.

Example:

var HelloWorld = Class.create();
HelloWorld.prototype = {
  initialize: function() {},
  sayHello: function() {
    return "Hello, World!";
  },
  type: 'HelloWorld'
};

7. How do you call a Script Include from a Client Script?

Answer:

You can use GlideAjax to call server-side Script Includes from Client Scripts.

Example:

var ga = new GlideAjax('HelloWorld');
ga.addParam('sysparm_name', 'sayHello');
ga.getXMLAnswer(function(response){
  alert(response);
});

In Short:

Script Type	Place	Language	Example
Client Script	Browser	JavaScript	`g_form.setValue()`
Business Rule	Server	JavaScript	`current.update()`
Script Include	Server	JavaScript	`Class.create()`

Welcome to ServiceNow - course

Guru prasanna — Fri, 25 Apr 2025 13:21:22 +0000

ServiceNow

ServiceNow is a cloud-based platform that helps organizations manage their IT services, business workflows, and operations in one centralized system.

Originally built for IT Service Management (ITSM), it has grown into a full enterprise platform for digital workflows.

Navigate to the User Menu (select the System Administrator avatar in the top right corner).
Select Impersonate user.
Locate and select Platform User [platform.user].
Complete the impersonation request by selecting the Impersonate user button.
Select and pin the 'All' menu so it is always present as you walk through tasks.
Navigate to Self-Service > Knowledge, explore the homepage.
Favorite the Knowledge module in order to easily locate it again in the future.
Ask yourself: what applications are available to you as the Platform User?

Lists and Filters

A list displays a set of records from a table. You can identify table data in the form of rows and columns. Each row represents one record. Each column represents one field.

Lists can be filtered and customized to display the information you need.

--> The list editor allows direct editing of field values in a list without opening a form.

Editing Process:

Open Editor: Double-click an empty area of the field or enable single-click editing.
Enter Values: Input the desired values.
Save Changes: Use the save icon, cancel icon, or press the Escape key to retain original values.
Keyboard Navigation: Use Tab and arrow keys to navigate fields.
Multi-line Text: Press Shift + Enter to add a new line.
Save Options:
- Press Enter to save and move to the next field.
- Use Ctrl + Enter for immediate save.
- Press Esc to close without saving.

Breadcrumb:

--> A breadcrumb is a navigation aid used primarily in lists and filters.
--> It visually displays the current filter conditions applied to a list and allows users to quickly modify or remove parts of the filter.

List filters

A filter is a set of conditions applied to a table list to isolate a subset of data. Three components that make up a filter condition include
[1] field,
[2] operator, and
[3] value.
Select the Show/hide filter (funnel) icon to add, remove, or edit filter conditions and apply them.

1. Field: A choice list based on the table and user access rights. The choice list includes fields on related tables by dot-walking.

2. Operator: A choice list based on the field type. For example, in the incident table, the greater than operator does not apply to the Active field but it does apply to the Priority field.

3. Value: A text entry field or a choice list, depending on the field type. For example, in the Incident table, the Active field offers a choice list with values true, false, and empty, while the Short description field offers a text entry field.

ServiceNow - Important Terms

Guru prasanna — Thu, 24 Apr 2025 10:09:47 +0000

Terms used in serviceNow:

Instance – Your own version of the ServiceNow platform.
Table – Stores data, similar to a spreadsheet.
Record – A single entry in a table (like one incident).
Field – A column in the table (like “Priority” or “Status”).
Form – The screen you use to view or edit a single record.
List – Displays multiple records from a table.
Module – A menu item that opens a table, form, list, or other feature.
Application – A collection of modules with a common purpose (e.g., Incident Management).
UI (User Interface) – The parts of ServiceNow you interact with (menus, forms, lists).
Filter / Breadcrumb – Used to search and narrow down data in a list.

Technical Terms:

Client Script – JavaScript that runs in the browser for form validation or automation.
Business Rule – Server-side script that runs when records are created, updated, or deleted.
UI Policy – Controls field behavior like visibility, read-only, or mandatory.
Catalog Item – A requestable item (like “Request Laptop”) in the Service Catalog.
Workflow / Flow – Automation that performs a series of steps based on conditions.
GlideRecord – A script API used to query or manipulate data on the server.
ACL (Access Control List) – Security rules that control access to data.
Update Set – A saved collection of changes that can be moved between instances.
SLA (Service Level Agreement) – Defines how long a task should take (e.g., resolve a ticket within 24 hours).

Common Tables used:

incident – For IT issue tracking.
change_request – For change management.
task – General table for tasks.
cmdb_ci – Stores configuration items.
sys_user – Stores user information.

About Linux - Compiler , Process ,Executable

Guru prasanna — Wed, 23 Apr 2025 07:52:48 +0000

Why linux?

--> Every code run in linux machine.
--> Linux is efficient due to its command line/Terminal.

Linux commands for renaming multiple images at a time:

--> ls img_*.jpg|sed
--> mv

In terminal for manual(To know about a command)
--> man sh

After knowing about commands then we can start scripting which can lead to devops.

To know how many mount point?

findmnt --real

partition:(About home directory)
mvmvp0 p1 p2

ls /usr/bin/ --> To store all executable
ls /usr/bin/ls

To view Task manager:

top
--> Now to exit from this click q.

How to create executable?

1) type gcc
--> If not found sudo apt install gcc
c source to convert file into executable.
2) gcc helloworld.c
3) Then remove conio.h line and again run.
4) You will get this error:

warning: implicit declaration of function ‘getch’; did you mean ‘getc’?

5) Run this code in terminal:

#include <stdio.h>
int main() {
printf("hello world\n");
return 0;
}

6) a.out --> Command not found
7) echo $PATH --> not in that directory
8) ./a.out --> Runs file inside current folder
9) echo $$ --> 3401

So using gcc we have compiled c code and converted to executable and then to run the file we used ./a.out and maked it process.

While running this code:

1) fork --> a.out
2) exec

Name change:
Before we have not specified name and now we are specifying name as helloworld and we can run with this name.

10) gcc -ohelloworld helloworld.c
11) ./helloworld --> File will be executed

Python programs for interview preparation

Guru prasanna — Tue, 22 Apr 2025 07:10:17 +0000

1. Check if a number is even or odd

num = int(input("Enter a number: "))
if num % 2 == 0:
    print("Even number")
else:
    print("Odd number")

2. Find the largest among three numbers

a = int(input("Enter first number: "))
b = int(input("Enter second number: "))
c = int(input("Enter third number: "))

if a >= b and a >= c:
    largest = a
elif b >= a and b >= c:
    largest = b
else:
    largest = c

print("The largest number is", largest)

3. Check if a string is a palindrome

s = input("Enter a string: ")

if s == s[::-1]:
    print("Palindrome")
else:
    print("Not a palindrome")

4. Print Fibonacci series up to N terms

n = int(input("Enter number of terms: "))
a, b = 0, 1
for i in range(n):
    print(a, end=" ")
    a, b = b, a + b

5. Factorial of a number (using loop)

num = int(input("Enter a number: "))
fact = 1

for i in range(1, num + 1):
    fact *= i

print("Factorial is", fact)

6. Check if a number is prime

num = int(input("Enter a number: "))

if num < 2:
    print("Not Prime")
else:
    for i in range(2, int(num**0.5)+1):
        if num % i == 0:
            print("Not Prime")
            break
    else:
        print("Prime Number")

7. Reverse a string

s = input("Enter a string: ")
rev = s[::-1]
print("Reversed string:", rev)

8. Sum of digits of a number

num = int(input("Enter a number: "))
total = 0
while num > 0:
    total += num % 10
    num = num // 10

print("Sum of digits:", total)

9. Find the second largest number in a list

numbers = [10, 25, 5, 100, 50]
numbers.sort()
print("Second largest:", numbers[-2])

10. Count vowels in a string

s = input("Enter a string: ")
vowels = "aeiouAEIOU"
count = 0

for char in s:
    if char in vowels:
        count += 1

print("Number of vowels:", count)

11. sum of digits repeatedly until the number becomes a single digit

def sum_of_digits(num):
    while num >= 10:
        total = 0
        while num > 0:
            total += num % 10
            num = num // 10
        num = total
    return num

number = int(input("Enter a number: "))
result = sum_of_digits(number)
print("Single digit sum is:", result)

12. Reverse a number (e.g., 123 → 321)

num = int(input("Enter a number: "))
rev = 0

while num > 0:
    digit = num % 10
    rev = rev * 10 + digit
    num = num // 10

print("Reversed number:", rev)

13. Find sum of elements in a list using sum() and without sum()

Using built-in:

lst = [1, 2, 3, 4, 5]
print("Sum:", sum(lst))

Without built-in:

total = 0
for num in lst:
    total += num
print("Sum:", total)

14. Count frequency of each character in a string

s = input("Enter a string: ")
freq = {}

for char in s:
    freq[char] = freq.get(char, 0) + 1

for k, v in freq.items():
    print(k, ":", v)

ServiceNow - Interview Questions and Answers

Guru prasanna — Mon, 21 Apr 2025 10:07:47 +0000

ServiceNow

1. What is ServiceNow?

Answer:
ServiceNow is a cloud-based platform that helps organizations manage digital workflows, especially for IT services like incident management, request tracking, approvals, and automation.

2. What is an Incident in ServiceNow?

Answer:
An incident is an unplanned interruption or issue in a service. It’s tracked using the incident table to restore service as quickly as possible.

3. What is a ServiceNow Table?

Answer:
A table stores data in rows and columns. Every record in ServiceNow — incidents, users, changes — is stored in a table.

4. What is the difference between a Client Script and a Business Rule?

Answer:
Client Script

--> Runs in browser (client-side)

--> Used for form validation or behavior

Business Rule
--> Runs on server (backend)
--> Used to update data or send field notifications

5. What is a Record in ServiceNow?

Answer:
A record is a single entry in a table — like one incident or one user. It’s like a row in Excel.

6. What is a Form and a List in ServiceNow?

Answer:
--> A form shows one record at a time (like filling a ticket).

--> A list shows multiple records (like a table view).

7. What is a UI Policy?

Answer:
A UI Policy changes how fields look on the form — like making them mandatory, hidden, or read-only based on conditions.

8. What is the Service Catalog?

Answer:
The Service Catalog is a place where users can request items or services, like new laptops, software, or access. Each request can trigger workflows and approvals.

9. What is the use of Flow Designer in ServiceNow?

Answer:
Flow Designer allows you to create automated workflows visually — without coding. It’s used to build flows like approval chains or email notifications.

10. What is GlideRecord?

Answer:
GlideRecord is a server-side script in ServiceNow used to query and interact with database tables (similar to SQL in code).

Software Testing - Manual Testing ,Levels,Types

Guru prasanna — Sat, 22 Mar 2025 06:30:45 +0000

Manual Testing

Manual Testing is the process of testing software manually (without using automation tools) to find bugs. A tester plays the role of an end-user and executes test cases to ensure the application works as expected.

1. What is Software Testing?

Software testing is the process of checking whether a software application meets the required specifications and is free of defects. It ensures that the application behaves correctly, is reliable, and performs well.

Why is Testing Needed?

To find bugs before users face them.
To ensure the software meets user requirements.
To improve software quality.
To avoid financial and reputation loss due to software failures.

2. What is Manual Testing?

Manual testing is testing software without using automation tools. Testers check the application by clicking buttons, entering data, and verifying outputs.

Advantages of Manual Testing:

✔ Better for new applications that change frequently.

✔ Finds user experience issues that automation may miss.

✔ Cost-effective for small projects.

Disadvantages of Manual Testing:

❌ Time-consuming for large applications.

❌ More chance of human errors.

3. Types of Manual Testing

a) Black Box Testing(For testers)

The tester doesn’t need to know the internal code.
Tests based on user actions.
Example: Checking if a login form works by entering a username and password.

b) White Box Testing(For developers or automation testers)

The tester knows the internal code and tests how different parts of the program work.
Example: Checking if a function correctly calculates the sum of two numbers.

c) Grey Box Testing(For testers with partial code knowledge)

A mix of Black Box and White Box testing.
The tester knows some internal working of the application but tests it as an end-user.

4. Different Levels of Manual Testing

a) Unit Testing

Testing individual parts of the application (like a single function or module).
Example: Checking if the “Add to Cart” button works properly.

b) Integration Testing

Testing how different modules work together.
Example: Checking if the cart updates correctly when an item is added.

c) System Testing

Testing the entire application to ensure it meets requirements.
Example: Checking if an e-commerce website works from login to checkout.

d) User Acceptance Testing (UAT)

Done by end users or clients before releasing the software.
Example: A customer testing a banking app before it goes live.

5. Test Case & Test Scenario

Test Case:

A detailed step-by-step document to test a specific function.
Example:
- Test Case: Verify the login page
- Steps: Enter username, enter password, click login
- Expected Result: User should log in successfully

Test Scenario:

A high-level idea of what to test.
Example: “Test login functionality” (without detailed steps).

6. Defect Life Cycle (Bug Life Cycle)

When a tester finds a bug, it follows a lifecycle:

New → Bug is reported.
Assigned → Sent to a developer.
In Progress → Developer starts fixing it.
Fixed → Bug is resolved.
Retest → Tester checks if it is fixed.
Closed → If fixed, it is marked as closed.

7. Difference Between Manual & Automation Testing

Execution:

--> Manual Testing is performed by a human tester.
--> Automation Testing is done using scripts and tools like Selenium.

Speed:

--> Manual Testing is slower since it requires human effort.
--> Automation Testing is faster as scripts execute quickly.

Cost:

--> Manual Testing is cost-effective for small projects.
--> Automation Testing has a higher initial cost due to tool and script development.

Accuracy:

--> Manual Testing is prone to human errors.
--> Automation Testing is more accurate since it follows predefined scripts.

Best For:

--> Manual Testing is ideal for small projects, exploratory testing, and UI testing.
--> Automation Testing is best for large projects, repetitive tasks, and regression testing.

8. Common Manual Testing Tools

Although manual testing doesn’t use automation, testers may use tools for reporting and tracking defects.

✔ JIRA – Tracks bugs and test cases.

✔ TestRail – Manages test cases.

✔ Bugzilla – Reports and tracks defects.

Software Development Life Cycle (SDLC)

SDLC is the process of developing software in a structured way, ensuring that it meets user requirements and is of high quality.
Phases of SDLC:

Requirement Gathering & Analysis:

Collect requirements from the client.
Example: A client wants an online banking system.

Planning:

Decide the budget, timeline, and resources needed for the project.

Design:

Create system architecture and UI/UX designs.
Example: Designing how the login page will look.

Development (Coding):

Developers write the code based on the design.

Testing:

Testers check for bugs and defects.
Example: Checking if the login works correctly.

Deployment:

The software is released for users.

Maintenance:

Fixing bugs and updating features after release.
Example: Fixing issues reported by users.

Software Testing Life Cycle (STLC)

STLC is a step-by-step process followed by testers to ensure the software is free of bugs and meets requirements.
Phases of STLC:

Requirement Analysis:

Testers understand what needs to be tested.
Example: Checking login, payments, and UI elements in a banking app.

Test Planning:

Create a test strategy and decide testing timelines.

Test Case Development:

Write test cases (step-by-step instructions for testing).

Test Environment Setup:

Prepare hardware, software, and test data for testing.

Test Execution:

Execute test cases and report bugs.

Test Closure:

Prepare a report summarizing the testing process and defects found.

Difference Between SDLC & STLC

SDLC is about software development, whereas STLC is about software testing.
SDLC includes coding, but STLC focuses only on testing.
STLC starts after SDLC’s requirement phase and runs in parallel with development.

9. Common Interview Questions on Manual Testing

1. What is the difference between testing and debugging?

Testing is finding defects; debugging is fixing them.

2. What are the qualities of a good tester?

Attention to detail, patience, analytical thinking, communication skills.

3. What is a test plan?

A document outlining what to test, how to test, and who will test.

Python - Theory Questions and Answers

Guru prasanna — Wed, 19 Mar 2025 07:55:16 +0000

1. Introduction to Python

Python is a high-level, interpreted, dynamically typed, and object-oriented programming language.
It is widely used for web development, data science, automation, AI, and more.

Key Features:

Simple and easy-to-learn syntax.
Interpreted language (no need for compilation).
Dynamically typed (no need to declare variable types).
Extensive standard library support.
Supports multiple programming paradigms (Object-Oriented, Functional, and Procedural).

2. Python Data Types

Basic Data Types:

int → Integer values, e.g., x = 10
float → Decimal numbers, e.g., y = 3.14
str → Sequence of characters, e.g., name = "Python"
bool → Boolean values, True or False

Collection Data Types:

List → Ordered, mutable collection, e.g., fruits = ["apple", "banana"]
Tuple → Ordered, immutable collection, e.g., numbers = (1, 2, 3)
Set → Unordered, unique elements, e.g., s = {1, 2, 3}
Dictionary → Key-value pairs, e.g., student = {"name": "John", "age": 25}

3. Variables and Operators

Variables:

Variables store data and do not require explicit type declaration.
Example:

  x = 10  # Integer
  y = "Python"  # String

Operators:

Arithmetic: +, -, *, /, %, **, //
Comparison: ==, !=, >, <, >=, <=
Logical: and, or, not
Assignment: =, +=, -=, *=, /=
Membership: in, not in
Identity: is, is not

4. Control Flow Statements

Conditional Statements:

Used for decision-making.
Example:

  x = 10
  if x > 0:
      print("Positive")
  elif x == 0:
      print("Zero")
  else:
      print("Negative")

Loops:

For Loop: Iterates over a sequence.

  for i in range(5):
      print(i)  # Output: 0 1 2 3 4

While Loop: Repeats a block of code while a condition is true.

  x = 0
  while x < 5:
      print(x)
      x += 1

Loop Control Statements:

break → Exits the loop early.
continue → Skips the current iteration.
pass → Placeholder for future code.

5. Functions in Python

Functions help reuse code and improve modularity.
Example:

  def greet(name):
      return "Hello, " + name

  print(greet("John"))  # Output: Hello, John

Lambda (Anonymous) Functions:

  square = lambda x: x * x
  print(square(4))  # Output: 16

6. Object-Oriented Programming (OOP) in Python

Key OOP Concepts:

Class & Object:

  class Person:
      def __init__(self, name, age):
          self.name = name
          self.age = age

      def greet(self):
          return f"Hello, my name is {self.name}"

  p1 = Person("Alice", 25)
  print(p1.greet())  # Output: Hello, my name is Alice

Encapsulation: Hiding data inside classes.
Inheritance: Reusing features of a parent class.
Polymorphism: Using a single method name for different types.

7. Exception Handling

Used to handle runtime errors.
Example:

  try:
      x = 10 / 0
  except ZeroDivisionError:
      print("Cannot divide by zero")
  finally:
      print("Execution complete")

8. File Handling

Opening and Reading a File:

with open("file.txt", "r") as file:
    content = file.read()
    print(content)

Writing to a File:

with open("file.txt", "w") as file:
    file.write("Hello, Python!")

9. Python Modules and Packages

Modules are files with Python code (.py).

  import math
  print(math.sqrt(16))  # Output: 4.0

Creating a Custom Module:

  # mymodule.py
  def greet(name):
      return f"Hello, {name}"

  # main.py
  import mymodule
  print(mymodule.greet("Alice"))

10. Decorators in Python

Used to modify functions without changing their code.
Example:

  def decorator_function(original_function):
      def wrapper_function():
          print("Wrapper executed before", original_function.__name__)
          return original_function()
      return wrapper_function

  @decorator_function
  def display():
      print("Display function executed")

  display()

11. Python’s `map()`, `filter()`, and `reduce()` Functions

Using `map()`:

Applies a function to all elements of an iterable.

  nums = [1, 2, 3, 4]
  squared = list(map(lambda x: x**2, nums))
  print(squared)  # Output: [1, 4, 9, 16]

Using `filter()`:

Filters elements based on a condition.

  nums = [1, 2, 3, 4, 5]
  even = list(filter(lambda x: x % 2 == 0, nums))
  print(even)  # Output: [2, 4]

Using `reduce()`:

Performs a cumulative operation on elements.

  from functools import reduce
  nums = [1, 2, 3, 4]
  result = reduce(lambda x, y: x + y, nums)
  print(result)  # Output: 10

12. Python Memory Management

Python uses automatic garbage collection to manage memory.
Objects are deleted when their reference count becomes zero.
Example:

  import sys
  x = "Hello"
  print(sys.getrefcount(x))  # Output: Reference count of object

SQL Interview questions and answers

Guru prasanna — Mon, 17 Mar 2025 10:03:25 +0000

SQL Interview Questions & Answers:

1. What is SQL?

--> SQL (Structured Query Language) is used to store, retrieve, manage, and manipulate data in relational databases like MySQL, PostgreSQL, SQL Server, and Oracle.

2. What are the different types of SQL commands?

SQL commands are categorized into five types:

DDL (Data Definition Language): CREATE, ALTER, DROP, TRUNCATE (Defines database structure).
DML (Data Manipulation Language): SELECT, INSERT, UPDATE, DELETE (Manipulates data).
DCL (Data Control Language): GRANT, REVOKE (Controls user permissions).
TCL (Transaction Control Language): COMMIT, ROLLBACK, SAVEPOINT (Manages transactions).
DQL (Data Query Language): SELECT (Retrieves data).

3. What is the difference between DELETE, TRUNCATE, and DROP?

DELETE removes specific rows from a table and can be rolled back using ROLLBACK.
TRUNCATE removes all rows from a table but keeps its structure. It cannot be rolled back.
DROP removes the entire table, including its structure. It also cannot be rolled back.

4. What is the difference between WHERE and HAVING?

WHERE is used to filter rows before grouping.
HAVING is used to filter grouped data after GROUP BY.

Example:

SELECT department, COUNT(*) 
FROM employees 
WHERE salary > 30000  
GROUP BY department
HAVING COUNT(*) > 5;

5. What is a Primary Key and Foreign Key?

--> Primary Key uniquely identifies each record in a table. It cannot have duplicate or NULL values.
--> Foreign Key references the primary key of another table, maintaining relationships between tables.

Example:

CREATE TABLE Customers (
    customer_id INT PRIMARY KEY,
    name VARCHAR(100)
);

CREATE TABLE Orders (
    order_id INT PRIMARY KEY,
    customer_id INT,
    FOREIGN KEY (customer_id) REFERENCES Customers(customer_id)
);

6. What is the difference between UNION and UNION ALL?

UNION combines results from multiple queries and removes duplicates.
UNION ALL combines results without removing duplicates.

Example:

SELECT name FROM customers
UNION  
SELECT name FROM employees;

SELECT name FROM customers
UNION ALL 
SELECT name FROM employees;

7. What are Joins in SQL? Explain types.

Joins combine records from multiple tables based on a related column.

INNER JOIN: Returns matching records from both tables.
LEFT JOIN: Returns all records from the left table + matching records from the right table.
RIGHT JOIN: Returns all records from the right table + matching records from the left table.
FULL JOIN: Returns all records when there is a match in either table.
SELF JOIN: Joins a table with itself.
CROSS JOIN: Returns the Cartesian product of both tables.

Example of INNER JOIN:

SELECT customers.name, orders.order_id  
FROM customers  
INNER JOIN orders ON customers.customer_id = orders.customer_id;

8. What is an Index in SQL?

--> An index improves search performance by creating a lookup table for faster access.
--> However, it can slow down INSERT, UPDATE, and DELETE operations because the index must be updated.

Example:

CREATE INDEX idx_customer_name ON customers(name);

9. What are Aggregate Functions?

Aggregate functions perform calculations on multiple rows and return a single value.

COUNT() → Returns the number of rows.
SUM() → Returns the total sum.
AVG() → Returns the average value.
MIN() → Returns the smallest value.
MAX() → Returns the largest value.

Example:

SELECT department, COUNT(*) AS total_employees, AVG(salary) AS avg_salary
FROM employees
GROUP BY department;

10. What is the difference between GROUP BY and ORDER BY?

GROUP BY groups rows with the same values and is used with aggregate functions.
ORDER BY sorts the result set in ascending (ASC) or descending (DESC) order.

Example:

SELECT department, COUNT(*) 
FROM employees 
GROUP BY department 

SELECT name, salary 
FROM employees 
ORDER BY salary DESC;

11. What is a Subquery?

A subquery is a query inside another query, typically used in WHERE, FROM, or SELECT clauses.

Example:

SELECT name FROM employees
WHERE salary > (SELECT AVG(salary) FROM employees);

Executes the inner query first (AVG(salary)).
The outer query filters employees with a salary above the average.

OOPS - Interview Questions in python

Guru prasanna — Mon, 17 Mar 2025 08:57:59 +0000

OOPs (Object-Oriented Programming) Interview Questions in Python

1) What is Object-Oriented Programming (OOP)?

OOP is a programming paradigm based on the concept of objects, which contain data (attributes) and methods (functions). It allows for code reusability, modularity, and abstraction.

Key principles of OOP:

Encapsulation : Hiding data inside a class and restricting direct access.
Abstraction : Hiding implementation details and exposing only necessary parts.
Inheritance : Reusing code by creating a new class from an existing one.
Polymorphism : Having multiple forms of the same method (overloading & overriding).

2) What is a Class and an Object?

A class is a blueprint/template for creating objects.
An object is an instance of a class.

3) What is Encapsulation?

--> Encapsulation is the process of hiding data within a class and only allowing controlled access via methods.
--> In Python, we use private attributes (__varname) to enforce encapsulation.

4) What is Inheritance?

Inheritance allows a class (child class) to inherit attributes and methods from another class (parent class).

Types of inheritance:

Single Inheritance → A child class inherits from a single parent class.
Multiple Inheritance → A child class inherits from multiple parent classes.
Multilevel Inheritance → A child class inherits from a parent class, which itself inherits from another parent.
Hierarchical Inheritance → Multiple child classes inherit from a single parent class.
Hybrid Inheritance → A mix of two or more types of inheritance (e.g., multiple + multilevel).

5) What is Polymorphism?

Polymorphism allows different classes to use the same method name but behave differently.

6) What is Abstraction?

--> Abstraction means hiding implementation details and exposing only the required functionalities using abstract classes.
--> Python provides ABC (Abstract Base Class) to achieve abstraction.

7) What is the difference between Method Overloading and Method Overriding?

Method overloading : Same method name with different parameters in the same class.
Method Overriding : Same method name and same parameters in a parent-child relationship (Inheritance).

Python Programs - Interview Questions and Answers

Guru prasanna — Fri, 14 Mar 2025 13:25:57 +0000

1️⃣ Reverse a String
Program:


def reverse_string(s):
    return s[::-1]

# Example usage
print(reverse_string("hello"))  # Output: "olleh"

Explanation:

s[::-1] is slicing with a step of -1 which reverses the string.

2️⃣ Check if a Number is Prime
Program:

no = int(input("Enter a number: "))

if no < 2:
    print("Not Prime")
else:
    div = 2
    while div < no:
        if no % div == 0:
            print("Not Prime")
            break
        div += 1
    else:
        print("Prime")

Explanation:

A number is prime if it is only divisible by 1 and itself.
We check if number is divisible by 2 and if remainder is 0 then it is not prime number.

3️⃣ Find the Factorial of a Number
Program:


def factorial(n):
    if n == 0 or n == 1:
        return 1
    return n * factorial(n - 1)

# Example usage
print(factorial(5))  # Output: 120

Explanation:

`Uses recursion: factorial(n) = n * factorial(n-1), base case factorial(1) = 1.`

4️⃣ Check if a String is a Palindrome
Program:

def is_palindrome(s):
    return s == s[::-1]

# Example usage
print(is_palindrome("madam"))  # Output: True
print(is_palindrome("hello"))  # Output: False

Explanation:

Compares the string with its reverse to determine if it is a palindrome.

5️⃣ Fibonacci Series using Recursion
Program:

def fibonacci(n):
    if n <= 0:
        return 0
    elif n == 1:
        return 1
    else:
        return fibonacci(n - 1) + fibonacci(n - 2)

Example usage

print([fibonacci(i) for i in range(6)]) # Output: [0, 1, 1, 2, 3, 5]

Explanation:

Recursively calculates the Fibonacci sequence.

6️⃣ Find the Largest Element in a List
Program:


def find_largest(lst):
    return max(lst)

# Example usage
print(find_largest([3, 5, 2, 9, 1]))  # Output: 9

Explanation:

Uses Python’s built-in `max()` function.

7️⃣ Swap Two Variables Without a Temporary Variable
Program:


a, b = 5, 10
a, b = b, a
print(a, b)  # Output: 10, 5

Explanation:

Swaps values using tuple unpacking.

8️⃣ Count the Number of Vowels in a String
Program:

def count_vowels(s):
    return sum(1 for char in s.lower() if char in "aeiou")

# Example usage
print(count_vowels("Hello World"))  # Output: 3

Explanation:

Uses list comprehension and `sum()` to count vowels.

9️⃣ Remove Duplicates from a List
Program:


def remove_duplicates(lst):
    return list(set(lst))

# Example usage
print(remove_duplicates([1, 2, 2, 3, 4, 4, 5]))  # Output: [1, 2, 3, 4, 5]

Explanation:

Converts list to a set to remove duplicates, then back to a list.

🔟 Check if Two Strings are Anagrams
Program:

def are_anagrams(s1, s2):
    return sorted(s1) == sorted(s2)

# Example usage
print(are_anagrams("listen", "silent"))  # Output: True
print(are_anagrams("hello", "world"))  # Output: False

Explanation:

Anagrams have the same letters in different orders, so sorting both strings should yield the same result.