Command	Syntax	Example
SELECT	SELECT cols FROM table	SELECT first_name, email FROM customers
WHERE	WHERE condition	WHERE city = 'Mumbai'
ORDER BY	ORDER BY col [ASC\|DESC]	ORDER BY price DESC
LIMIT	LIMIT n [OFFSET m]	LIMIT 10 OFFSET 5
DISTINCT	SELECT DISTINCT col	SELECT DISTINCT city FROM customers
LIKE	WHERE col LIKE 'pattern'	WHERE email LIKE '%@gmail.com'
IN	WHERE col IN (val1, val2)	WHERE status IN ('pending', 'completed')
BETWEEN	WHERE col BETWEEN a AND b	WHERE price BETWEEN 1000 AND 5000
IS NULL	WHERE col IS NULL	WHERE phone IS NULL
CASE	CASE WHEN cond THEN val END	CASE WHEN price > 10000 THEN 'Premium' END
ALIAS	SELECT col AS alias	SELECT COUNT(*) AS total

Join Type	What It Returns	Use Case
INNER JOIN	Matching rows from both tables	Customer + their orders
LEFT JOIN	All left rows + matching right	All customers, even without orders
RIGHT JOIN	All right rows + matching left	All orders, even without customer (rare)
FULL OUTER JOIN	All rows from both tables	Find unmatched records on both sides
CROSS JOIN	Every combination (cartesian)	Generate all possible pairs
SELF JOIN	Table joined to itself	Find pairs, hierarchies, comparisons

Function	Purpose	Example
COUNT(*)	Count all rows	SELECT COUNT(*) FROM orders
COUNT(col)	Count non-NULL values	SELECT COUNT(phone) FROM customers
COUNT(DISTINCT col)	Count unique values	SELECT COUNT(DISTINCT city) FROM customers
SUM(col)	Total of values	SELECT SUM(total_amount) FROM orders
AVG(col)	Average of values	SELECT AVG(price) FROM products
MIN(col)	Smallest value	SELECT MIN(price) FROM products
MAX(col)	Largest value	SELECT MAX(total_amount) FROM orders
GROUP BY	Group rows for aggregation	GROUP BY category
HAVING	Filter groups (not rows)	HAVING COUNT(*) > 5

Function	Purpose	Syntax
ROW_NUMBER()	Unique sequential number	ROW_NUMBER() OVER (ORDER BY col)
RANK()	Rank with gaps for ties	RANK() OVER (ORDER BY col DESC)
DENSE_RANK()	Rank without gaps	DENSE_RANK() OVER (ORDER BY col DESC)
LAG(col, n)	Value from n rows before	LAG(order_date, 1) OVER (ORDER BY date)
LEAD(col, n)	Value from n rows after	LEAD(price) OVER (ORDER BY price)
SUM() OVER	Running total	SUM(amount) OVER (ORDER BY date)
AVG() OVER	Moving average	AVG(amount) OVER (ROWS 6 PRECEDING)
PARTITION BY	Window groups	OVER (PARTITION BY category ORDER BY price)

Command	Syntax	Example
INSERT	INSERT INTO table (cols) VALUES (vals)	INSERT INTO customers (first_name) VALUES ('Test')
UPDATE	UPDATE table SET col = val WHERE cond	UPDATE products SET price = 999 WHERE product_id = 1
DELETE	DELETE FROM table WHERE cond	DELETE FROM orders WHERE status = 'cancelled'

Command	Syntax	Example
CREATE TABLE	CREATE TABLE name (col type constraints)	CREATE TABLE users (id INT PRIMARY KEY)
ALTER TABLE	ALTER TABLE name ADD/MODIFY/DROP col	ALTER TABLE users ADD phone VARCHAR(15)
DROP TABLE	DROP TABLE name	DROP TABLE temp_data
TRUNCATE	TRUNCATE TABLE name	TRUNCATE TABLE logs
CREATE INDEX	CREATE INDEX name ON table(col)	CREATE INDEX idx_email ON customers(email)

Constraint	Purpose	Example
PRIMARY KEY	Unique row identifier	customer_id INT PRIMARY KEY
FOREIGN KEY	References another table	FOREIGN KEY (customer_id) REFERENCES customers(customer_id)
UNIQUE	No duplicate values	email VARCHAR(100) UNIQUE
NOT NULL	Cannot be empty	first_name VARCHAR(50) NOT NULL
CHECK	Value must satisfy condition	CHECK (price > 0)
DEFAULT	Fallback value if not provided	status VARCHAR(20) DEFAULT 'active'

SQL Cheat Sheet — Quick Reference

Data Query (DQL)