SQL Overview

Structured Query Language (SQL) is the standard language for relational database management systems. It enables you to create, read, update, and delete (CRUD) data, as well as manage database structures and control access.

Key Concepts

• Data Definition Language (DDL) – CREATE, ALTER, DROP
• Data Manipulation Language (DML) – SELECT, INSERT, UPDATE, DELETE
• Data Control Language (DCL) – GRANT, REVOKE
• Transaction Control – COMMIT, ROLLBACK, SAVEPOINT

Basic SELECT Example

SELECT
    FirstName,
    LastName,
    Email
FROM
    Users
WHERE
    IsActive = 1
ORDER BY
    LastName ASC;

Creating a Table

CREATE TABLE Employees (
    EmployeeID INT PRIMARY KEY,
    FirstName NVARCHAR(50) NOT NULL,
    LastName NVARCHAR(50) NOT NULL,
    HireDate DATE,
    Salary DECIMAL(10,2)
);

Resources

• SQL Tutorial – From Basics to Advanced
• SQL Reference – Full Syntax
• Built‑in Functions
• Performance Tuning Guide