SQL Commands Cheatsheet

1. DDL (Data Definition Language)

Commands used to define the database structure or schema.

CREATE

CREATE TABLE Students (
    ID int NOT NULL AUTO_INCREMENT,
    LastName varchar(255) NOT NULL,
    FirstName varchar(255),
    Age int,
    PRIMARY KEY (ID)
);

ALTER

ALTER TABLE Students
ADD Email varchar(255);

DROP

DROP TABLE Students; -- Deletes the entire table structure and data

2. DML (Data Manipulation Language)

Commands used for managing data within schema objects.

INSERT INTO

INSERT INTO Students (FirstName, LastName, Age)
VALUES ('John', 'Doe', 21);

UPDATE

UPDATE Students
SET Age = 22
WHERE FirstName = 'John' AND LastName = 'Doe';

DELETE

DELETE FROM Students
WHERE Age < 18;

3. DQL (Data Query Language)

SELECT

SELECT FirstName, Age FROM Students
WHERE Age > 20
ORDER BY LastName ASC
LIMIT 10;

JOIN (Inner Join)

SELECT Orders.OrderID, Customers.CustomerName
FROM Orders
INNER JOIN Customers ON Orders.CustomerID = Customers.CustomerID;