SQL is the language for managing and querying relational databases. Master these fundamentals for data management.
Basic SELECT Queries
-- Select all columns
SELECT * FROM users;
-- Select specific columns
SELECT name, email FROM users;
-- Filter with WHERE
SELECT * FROM users WHERE age >= 18;
-- Sort results
SELECT * FROM users ORDER BY name ASC;
Filtering and Conditions
-- AND, OR conditions
SELECT * FROM users
WHERE age >= 18 AND city = 'NYC';
-- IN operator
SELECT * FROM users
WHERE city IN ('NYC', 'LA', 'Chicago');
-- LIKE pattern matching
SELECT * FROM users
WHERE email LIKE '%@gmail.com';
JOIN Operations
-- INNER JOIN
SELECT users.name, orders.total
FROM users
INNER JOIN orders ON users.id = orders.user_id;
-- LEFT JOIN
SELECT users.name, orders.total
FROM users
LEFT JOIN orders ON users.id = orders.user_id;
Aggregation Functions
-- COUNT, SUM, AVG
SELECT COUNT(*) FROM users;
SELECT AVG(age) FROM users;
SELECT SUM(total) FROM orders;
-- GROUP BY
SELECT city, COUNT(*) as user_count
FROM users
GROUP BY city;
SQL is essential for working with data in most applications!