Difference Between SQL DELETE and SQL TRUNCATE

What is SQL?

SQL (Structured Query Language) is a standard programming language used to store, retrieve, manage, and manipulate data in relational databases. It is widely used in database management systems (DBMS) like MySQL, PostgreSQL, SQL Server, and Oracle.

Key Features of SQL :

* Declarative Language – You specify what you want, not how to do it.
* Relational Database Management – Works with structured data stored in tables.
* Data Manipulation & Querying – Retrieve and modify data efficiently.
* Scalability & Security – Supports large datasets and access control.

Types of SQL Commands :

SQL commands are categorized into five main types :

-- Create a table
CREATE TABLE employees (
    id INT PRIMARY KEY,
    name VARCHAR(50),
    department VARCHAR(50),
    salary DECIMAL(10,2)
);

-- Insert data into the table
INSERT INTO employees (id, name, department, salary)
VALUES (1, 'Alice', 'HR', 55000.00);

-- Retrieve data
SELECT * FROM employees;

-- Update a record
UPDATE employees SET salary = 60000 WHERE id = 1;

-- Delete a record
DELETE FROM employees WHERE id = 1;

Why Use SQL?

* Universal Standard – Used in almost all database systems
* Powerful & Flexible – Handles large datasets efficiently
* Easy to Learn – Simple syntax for querying and managing data
* Supports ACID Properties – Ensures Atomicity, Consistency, Isolation, Durability in transactions.

What is a SQL DELETE Command?

The DELETE command in SQL is used to remove specific records (rows) from a table based on a given condition. It allows selective deletion using the WHERE clause.

Syntax of DELETE :

DELETE FROM table_name WHERE condition;

* table_name – The name of the table from which you want to delete records.
* condition – Specifies which rows should be deleted.

If you omit the WHERE clause, all rows in the table will be deleted!

Example Usage

1. Deleting a Specific Row :

DELETE FROM employees WHERE id = 3;?

Deletes the row where id = 3 from the employees table.

2. Deleting Multiple Rows :

DELETE FROM employees WHERE department = 'Sales';?

Deletes all employees in the Sales department.

3. Deleting All Rows (Use with Caution!) :

DELETE FROM employees;?

DELETE FROM employees;

Removes all records from the employees table without deleting the table structure.

Key Features of DELETE :

What is a SQL TRUNCATE Command?

The TRUNCATE command in SQL is used to remove all records from a table efficiently. Unlike DELETE, it does not delete rows one by one but instead deallocates the entire table’s data pages, making it much faster.

Syntax of TRUNCATE :

TRUNCATE TABLE table_name;?

table_name – The name of the table from which all rows will be removed.

Example Usage :

* Removing All Records from a Table :

TRUNCATE TABLE employees;

This removes all records from the employees table but keeps the table structure intact.

Key Features of TRUNCATE :

Best Practices for Using TRUNCATE :

* Use TRUNCATE when you need to quickly remove all records from a table.
* Do not use TRUNCATE if you need to retain identity values or trigger actions.
* If you need to delete specific rows, use DELETE instead.

Key Differences Between DELETE and TRUNCATE :

When to Use?

• Use DELETE when you need to remove specific records while keeping the structure intact.
• Use TRUNCATE when you need to quickly remove all records without concern for rollback.

* Example Usage :

-- DELETE example (removes specific rows)
DELETE FROM employees WHERE department = 'Sales';

-- TRUNCATE example (removes all rows)
TRUNCATE TABLE employees;