?️ MySQL DELETE

? Quick Overview

The DELETE statement in MySQL is used to remove one or more records from a table. When working with PHP and MySQL, this command is commonly executed through database queries to permanently remove unwanted data.

? Key Concepts

• DELETE removes rows permanently
• WHERE controls which rows are removed
• Without WHERE, all records are deleted
• Commonly used with PHP database APIs like mysqli or PDO

? Syntax / Theory

// Basic DELETE syntax in MySQL
DELETE FROM table_name WHERE condition;

? Example 1: Delete a Single Row

This query deletes the employee whose ID is 5 from the employees table.

// Delete a specific employee by ID
DELETE FROM employees WHERE employee_id = 5;

? Example 2: Delete Multiple Rows

This query removes all employees earning less than 30000.

// Delete employees with low salary
DELETE FROM employees WHERE salary < 30000;

⚠️ Delete All Rows

Omitting the WHERE clause deletes every record in the table while keeping the table structure intact.

// Delete all records from employees table
DELETE FROM employees;

? PHP + MySQL DELETE Example

This example demonstrates executing a DELETE query using PHP and MySQLi.

// PHP code to delete a record using MySQLi
$conn = mysqli_connect("localhost","root","","company");
$sql = "DELETE FROM employees WHERE employee_id = 5";
mysqli_query($conn,$sql);

? Interactive Concept

Think of DELETE as a filter + eraser. The WHERE clause selects rows, and MySQL erases only those rows. No undo is available unless a backup exists.

? Use Cases

• Removing inactive users
• Clearing expired sessions
• Deleting obsolete records
• Cleaning up test data