SQL Basics

Learn the four core SQL operations (CRUD) plus filtering, sorting, and limiting. Practice on a sample SQLite database.

SQLSELECTCRUDWHEREORDER BY

Duration

⏱ About 2 hours

Level

📊 Beginner+

Prerequisite

🎯 db-01

OUTCOME

Read and write data in any SQL database with the four core verbs

What you'll learn

1Run SELECT queries with WHERE, ORDER BY, LIMIT
2INSERT new rows safely
3UPDATE and DELETE with WHERE
4Use comparison and logical operators correctly

1. SELECT

sql

SELECT * FROM users;
SELECT name, email FROM users;

SELECT name FROM users
WHERE age >= 18 AND city = 'Seoul'
ORDER BY name ASC
LIMIT 10;

2. INSERT

sql

INSERT INTO users (name, email, age)
VALUES ('Alice', 'alice@example.com', 30);

-- Multiple rows
INSERT INTO users (name, email) VALUES
  ('Bob',   'bob@example.com'),
  ('Carol', 'carol@example.com');

3. UPDATE & DELETE

sql

UPDATE users SET age = 31 WHERE id = 1;

DELETE FROM users WHERE id = 2;

⚠️

Always include WHERE on UPDATE and DELETE — without it, the change affects every row in the table.

4. Operators

Operator	Example
=, <>	WHERE id = 1, WHERE status <> 'done'
<, <=, >, >=	WHERE age >= 18
AND, OR, NOT	WHERE a = 1 AND b = 2
IN	WHERE city IN ('Seoul', 'Busan')
BETWEEN	WHERE price BETWEEN 100 AND 200
LIKE	WHERE name LIKE 'A%' (starts with A)
IS NULL	WHERE deleted_at IS NULL

Example code / lecture materials

All lecture materials and example code are openly available on GitHub.

View on GitHub ↗