DML

📘 What is DML (Data Manipulation Language)?

DML (Data Manipulation Language) is the part of SQL used to interact with the actual data stored in tables — reading, inserting, updating, and deleting records.

If the database structure (tables, columns) is a house built using DDL, then DML is how you live in it — putting stuff in, changing things around, or throwing stuff out.

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🔧 Key DML Commands:

Command	What It Does
SELECT	Retrieves data from one or more tables
INSERT	Adds new rows to a table
UPDATE	Modifies existing rows in a table
DELETE	Removes rows from a table

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🛠️ Example Usage:

1. INSERT

INSERT INTO users (id, name, email)
VALUES (1, 'Gaurav', 'gaurav@example.com');

Adds a new row to the users table.

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2. SELECT

SELECT name, email FROM users WHERE id = 1;

Fetches specific data from the table.

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3. UPDATE

UPDATE users SET email = 'new@email.com' WHERE id = 1;

Changes the email of the user with ID 1.

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4. DELETE

DELETE FROM users WHERE id = 1;

Deletes the user with ID 1 from the table.

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🧪 DML + Transactions:

DML operations can be rolled back using TCL (Transaction Control Language):

BEGIN;
DELETE FROM users WHERE id = 1;
ROLLBACK; -- undoes the delete

So, DML changes are not permanent until committed.

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⚠️ DML vs DDL:

Feature	DDL	DML
Affects	Structure (schema)	Data (rows/records)
Auto-commit	Yes	No (can rollback)
Example	CREATE TABLE	INSERT INTO table

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🧠 Interview Line:

“DML allows users to interact with data using SELECT, INSERT, UPDATE, and DELETE. Unlike DDL, DML operations are transactional and can be committed or rolled back.”