Introduction to SQL

Database म्हणजे organized data चा collection. Applications सगळा data database मध्ये store करतात — users, orders, products सगळे. SQL (Structured Query Language) म्हणजे database शी communicate करायची भाषा.

Database चे प्रकार

• ▸Relational Database (RDBMS) — data tables मध्ये, rows आणि columns — MySQL, PostgreSQL, SQLite, Oracle
• ▸NoSQL Database — documents, key-value, graphs — MongoDB, Redis, Cassandra
• ▸SQL मुख्यतः Relational databases साठी वापरतात

SQL Commands चे प्रकार

• ▸DDL (Data Definition Language) — CREATE, ALTER, DROP, TRUNCATE — structure define करतो
• ▸DML (Data Manipulation Language) — INSERT, UPDATE, DELETE — data modify करतो
• ▸DQL (Data Query Language) — SELECT — data read करतो
• ▸DCL (Data Control Language) — GRANT, REVOKE — permissions
• ▸TCL (Transaction Control) — COMMIT, ROLLBACK — transactions

-- हे एक SQL comment आहे
-- Database बनवणे
CREATE DATABASE school;

-- Database वापरणे
USE school;

-- Table बनवणे
CREATE TABLE students (
    id   INT PRIMARY KEY AUTO_INCREMENT,
    name VARCHAR(100) NOT NULL,
    city VARCHAR(50),
    marks INT
);

-- Data insert करणे
INSERT INTO students (name, city, marks)
VALUES ('Rahul Patil', 'Pune', 85);

-- Data वाचणे
SELECT * FROM students;