SQL Cheat Sheet: Queries Every Developer Should Know

Basic SQL Queries

-- Select all columns
SELECT * FROM users;

-- Select specific columns
SELECT id, name, email FROM users;

-- Filter with WHERE
SELECT * FROM users WHERE active = true;

-- Sort results
SELECT * FROM users ORDER BY created_at DESC;

-- Limit results
SELECT * FROM users LIMIT 10 OFFSET 20;

Joins

-- INNER JOIN (only matching rows)
SELECT u.name, o.total
FROM users u
INNER JOIN orders o ON u.id = o.user_id;

-- LEFT JOIN (all users, even without orders)
SELECT u.name, COUNT(o.id) as order_count
FROM users u
LEFT JOIN orders o ON u.id = o.user_id
GROUP BY u.id, u.name;

Aggregations

SELECT
  COUNT(*) as total,
  AVG(price) as avg_price,
  MAX(price) as max_price,
  SUM(quantity) as total_qty
FROM products;

Common String Functions

SELECT UPPER(name), LOWER(email), LENGTH(bio)
FROM users;

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