SQL Commands Cheatsheet — SELECT, JOIN, GROUP BY & More

SQL commands cheatsheet.

Query, filter, aggregate, join and modify — the core SQL statements, ready to copy and adapt.

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Querying

SELECT * FROM table;Return every column and row from a table

SELECT col1, col2 FROM table;Return only specific columns

SELECT * FROM table WHERE col = 'x';Filter rows by a condition

SELECT DISTINCT col FROM table;Return unique values of a column

SELECT * FROM table ORDER BY col DESC;Sort results by a column

SELECT * FROM table LIMIT 10;Return at most 10 rows

Aggregating

SELECT COUNT(*) FROM table;Count the rows in a table

SELECT col, COUNT(*) FROM table GROUP BY col;Count rows per group

SELECT AVG(col) FROM table;Average a numeric column

SELECT col, SUM(amt) FROM table GROUP BY col HAVING SUM(amt) > 100;Filter groups by an aggregate

Joining

SELECT * FROM a JOIN b ON a.id = b.a_id;Inner join two tables on a key

SELECT * FROM a LEFT JOIN b ON a.id = b.a_id;Keep all rows from the left table

SELECT * FROM a, b WHERE a.id = b.a_id;Older comma-style join syntax

Modifying

INSERT INTO table (a, b) VALUES (1, 'x');Add a new row

UPDATE table SET col = 'x' WHERE id = 1;Change values in matching rows

DELETE FROM table WHERE id = 1;Remove matching rows

CREATE TABLE t (id INT, name TEXT);Create a new table

ALTER TABLE t ADD COLUMN c INT;Add a column to a table

DROP TABLE t;Delete a table and its data

These use standard ANSI SQL syntax; a few details (LIMIT vs TOP, quoting) vary between PostgreSQL, MySQL, SQLite and SQL Server.

The statements behind every query

Most SQL work is built from a few patterns: SELECT … WHERE to read and filter, GROUP BY with aggregates like COUNT and SUM to summarise, JOIN to combine tables, and INSERT/UPDATE/DELETE to change data. Swap in your own table and column names as you copy.

FAQ

What's the difference between INNER JOIN and LEFT JOIN?

INNER JOIN returns only rows with a match in both tables; LEFT JOIN returns all rows from the left table and fills in NULLs where the right table has no match.

How do I limit the number of rows returned?

Use LIMIT 10 in PostgreSQL, MySQL and SQLite. SQL Server uses SELECT TOP 10 … instead.

SQL commands cheatsheet.

The statements behind every query

FAQ

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