Introduction

purpose ,  different types of , use of the , difference between PHP  function var_dump() data types isset() == and ===  array include() and require()   constant $_POST (use of, )  different types of loops purpose of the break statement connect to a MySQL database?(how)  fetch data from a MySQL database(how)  session  $_GET  (use of the) superglobals handle file uploads(how) GET vs POST  send email cookies? header()  $_FILES redirect a user prepared statements handle errors  __construct()  OOP use of the parent::__construct()  method abstract class traits PDO  handle a database connection using PDO namespaces regular expressions dependency injection implement autoloading  public vs private vs  protected  use of the __sleep() and __wakeup() methods SOLID principles perform database transactions  static and dynamic methods final keyword RESTful API? design patterns handle file syst...

 QUERY SELECT 1️⃣ Basic SELECT Query SELECT * FROM table_name; 🔹 Retrieves all columns from the table. 2️⃣ Selecting Specific Columns SELECT column1, column2 FROM table_name; 🔹 Retrieves only the specified columns. 3️⃣ Using WHERE Clause (Filter Data) SELECT * FROM table_name WHERE column_name = 'value'; 🔹 Fetch records where column_name matches 'value' . 4️⃣ Sorting Results (ORDER BY) SELECT * FROM table_name ORDER BY column_name ASC;  -- Ascending Order SELECT * FROM table_name ORDER BY column_name DESC; -- Descending Order 🔹 Sorts data in ascending or descending order. 5️⃣ Filtering with Multiple Conditions (AND/OR) SELECT * FROM table_name WHERE column1 = 'value1' AND column2 = 'value2'; SELECT * FROM table_name WHERE column1 = 'value1' OR column2 = 'value2'; 🔹 Uses AND (both conditions must be true) or OR (either condition can be true). 6️⃣ Using LIKE (Pattern Matching) SELECT * FROM table_name WHERE column_name LIKE 'A%...

  SQL Interview Questions Only (Organized for Preparation) Beginner Level (20 Questions) What is SQL? What are the different types of SQL commands? What is the difference between DDL and DML? What is a Primary Key? What is a Foreign Key? What is a Unique Key? What is the difference between WHERE and HAVING clause? What is a NULL value in SQL? What is a constraint? What are indexes in SQL? How to fetch unique records from a table? What is the difference between DELETE and TRUNCATE? What is the purpose of the GROUP BY clause? What is a View in SQL? What is normalization? What are the types of normalization? What is the use of the ORDER BY clause? What are aggregate functions in SQL? What is a default constraint? What are aliases in SQL? Intermediate Level (20 Questions) What are the types of JOINs in SQL? Explain INNER JOIN with an example. Explain LEFT JOIN with an example. Explain RIGHT JOIN with an examp...

 Level               Type Advanced  1. How to optimize a slow query? ➤ Use indexing, avoid SELECT *, use WHERE clauses properly. 2. What is indexing and its types? ➤ Single column index, Composite index, Unique index, Full-text index. 3. What is a partitioned table? ➤ A table divided into multiple pieces for better management and performance. 4. How does indexing impact INSERT and UPDATE? ➤ Indexing can slow down INSERT and UPDATE due to additional overhead. 5. Explain CTE (Common Table Expressions)? ➤ Temporary result set that can be referenced within a query. 6. What is window function in SQL? ➤ Functions like ROW_NUMBER(), RANK(), used across a set of rows related to the current row. 7. What is replication in SQL? ➤ Copying data from one database to another automatically. 8. Difference between clustered and non-clustered index? ➤ Clustered index sorts data physically; non-clustered uses a separate structure. 9. How to ...

 Level               Type 1. Difference between INNER JOIN and LEFT JOIN? ➤ INNER JOIN returns matching rows, LEFT JOIN returns all rows from the left table. 2. What is a stored procedure? ➤ A saved collection of SQL statements that can be executed repeatedly. 3. What is a trigger? ➤ A trigger automatically performs actions in response to events on a table. 4. What is an alias in SQL? ➤ Temporary name for a table or column. 5. What is UNION and UNION ALL? ➤ UNION removes duplicates, UNION ALL includes all records. 6. How to prevent SQL injection? ➤ Use prepared statements and parameterized queries. 7. What is ACID property? ➤ Atomicity, Consistency, Isolation, Durability — ensures safe database transactions. 8. What is a transaction? ➤ A sequence of operations performed as a single logical unit of work. 9. How to update data in a table? ➤ Using UPDATE statement. 10. What is a composite key? ➤ A key made of two or more colum...

 Level                  Type      Beginner                             Basics (Database, Tables, Basic Queries) 📌 Key Topics You Must Prepare for SQL: SQL Basics – What is SQL, Commands (DDL, DML, DCL, TCL, DQL) Tables and Keys – Primary Key, Foreign Key, Composite Key Basic Queries – SELECT, WHERE, ORDER BY, GROUP BY, HAVING Joins – INNER JOIN, LEFT JOIN, RIGHT JOIN, FULL JOIN Subqueries – Simple and Correlated Constraints – NOT NULL, UNIQUE, CHECK, DEFAULT Normalization – 1NF, 2NF, 3NF Indexes – Clustered, Non-Clustered Transactions – COMMIT, ROLLBACK, SAVEPOINT, Isolation Levels Views – Virtual tables using SELECT queries Stored Procedures, Functions, and Triggers Optimization Techniques – Indexing, Query Tuning Window Functions – ROW_NUMBER(), RANK(), DENSE_RANK() Backup and R...

  🔹 1. Simple Login System 🧠 Focus On: HTML form $_POST Password hashing & password_verify() Sessions ( session_start() ) ✅ Must Know: How to validate and authenticate user credentials. 🔹 2. User Registration with Validation 🧠 Focus On: Form submission Email validation Password match Insert into MySQL ✅ Must Know: Email format check using filter_var() , required fields, hash password with password_hash() . 🔹 3. CRUD Application (Create, Read, Update, Delete) 🧠 Focus On: MySQLi connection Insert, select, update, delete queries URL query string for edit/delete actions ✅ Must Know: Build full CRUD using plain PHP & MySQL (with mysqli_* functions or PDO). 🔹 4. File Upload Script (Image Upload) 🧠 Focus On: File form with enctype="multipart/form-data" Validate file type/size Move file to uploads/ folder ✅ Must Know: Handle $_FILES , use move_uploaded_file() , validate extension and size. 🔹 5. F...

Level              Type Advanced                          OOP, MySQL integration, validation, security, APIs, error handling 1. What is OOP in PHP? ➤ Object-Oriented Programming allows organizing code using classes and objects. 2. What are classes and objects? ➤ A class is a blueprint; objects are instances of a class. 3. What is inheritance in PHP? ➤ One class can inherit methods and properties from another class using extends 4. What is an interface in PHP? ➤ Defines methods a class must implement. 5. What are constructors and destructors? ➤ __construct() runs when an object is created, __destruct() runs when it is destroyed. 6. What is abstraction? ➤ Hiding internal details and showing only the functionality. 7. What is encapsulation? ➤ Restricting access to class members using private/protected/public. 8. What is a trait in PHP?...

Level          Type Level                                    Arrays, forms, sessions, cookies, file handling, string/date functions 1. What is a PHP session? ➤ Used to store user data across multiple pages. 2. How do you start a session? ➤ Use session_start(); 3.What is a cookie? ➤ Stores small data on the client-side; use setcookie() . 4. How to send a form using PHP? ➤ Use method="post" or method="get" and handle with $_POST or $_GET . 5. How to upload a file in PHP? ➤ Use enctype="multipart/form-data" and handle with $_FILES . 6. How to handle a checkbox or radio in PHP? ➤ Use isset($_POST['checkbox_name']) to check selection. 7. What is the use of explode() function? ➤ Splits a string into an array using a delimiter. 8. What is implode() ? ➤ Joins array elements into a string. 9. How to redirect a page in PHP? ➤ Using h...

 Level           Type Beginner                     Basics (syntax, variables, data types, operators, loops, functions) 1. What is PHP? ➤ PHP is a server-side scripting language used to create dynamic web pages. 2. How to declare a variable in PHP? ➤ Using $ $name = "Lakshmi"; 3. What are PHP data types? ➤ PHP data types are like Integer, Float, String, Boolean, Array, Object, NULL, and Resource — used to define what kind of data a variable stores. ➤You can check a variable's data type using var_dump($variable); ➤ String, Integer, Float, Boolean, Array, Object, NULL. 4. How do you write comments in PHP? ➤ Single-line: // , multi-line: /* comment */ 5. What is the difference between echo and print ? ➤ Both echo and print are used to display output in PHP ➤  echo can output multiple values, faster. print returns 1, usable in expressions. 6. How to write a function in ...