SQL > Data Manipulation Language (DML)

Introduction

Data Manipulation Language (DML) is a subset of SQL used to insert, update, delete, and retrieve data from a database. Unlike DDL, which defines the structure, DML operates on the data within the tables.

Key DML Commands:

SELECT

Purpose:

The SELECT command is used to retrieve data from one or more tables.

Syntax:

SELECT column1, column2 FROM table_name WHERE condition;

Examples:

Retrieve all columns from a table:

SELECT * FROM Employees;

Retrieve specific columns:

SELECT FirstName, LastName FROM Employees;

Using WHERE clause:

SELECT * FROM Employees WHERE Age > 30;

INSERT

Purpose:

The INSERT command is used to add new records to a table.

Syntax:

INSERT INTO table_name (column1, column2) VALUES (value1, value2);

Examples:

Insert a single record:

INSERT INTO Employees (EmployeeID, FirstName, LastName, Age, Salary)
VALUES (1, 'John', 'Doe', 30, 50000);

Insert multiple records:

INSERT INTO Employees (EmployeeID, FirstName, LastName, Age, Salary)
VALUES
(2, 'Jane', 'Smith', 28, 60000),
(3, 'Mark', 'Taylor', 35, 70000);

UPDATE

Purpose:

The UPDATE command modifies existing records in a table.

Syntax:

UPDATE table_name SET column1 = value1 WHERE condition;

Examples:

Update a single column:

UPDATE Employees SET Salary = 75000 WHERE EmployeeID = 3;

Update multiple columns:

UPDATE Employees SET Salary = 80000, Age = 36 WHERE EmployeeID = 3;

DELETE

Purpose:

The DELETE command removes records from a table.

Syntax:

DELETE FROM table_name WHERE condition;

Examples:

Delete a specific record:

DELETE FROM Employees WHERE EmployeeID = 1;

Delete all records from a table (use with caution):

DELETE FROM Employees;

Summary

Command Description
SELECT Retrieves data from a table.
INSERT Adds new records to a table.
UPDATE Modifies existing records in a table.
DELETE Removes records from a table.

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