SQL Cheatsheet - Common Query Syntax & Examples

For developers who write SQL that is both business-correct and fast. The traps are usually not in the syntax itself but in NULL propagation, filtering after GROUP BY requiring HAVING, and where window functions stop overlapping plain aggregation. By the end you can write correct queries with grouping and filtering clauses, use window functions for row numbers and in-group ranking instead of self-joins, dodge NULL comparisons and aggregation pitfalls, and wrap multi-statement work in transactions for atomicity.

Databases·35 commands·Last updated 2026-08-02

Basic Query 6

SELECT * FROM users

Select all columns

SELECT name, age FROM users

Select specific columns

SELECT * FROM users WHERE age > 18

Filter with condition

SELECT DISTINCT city FROM users

Remove duplicates

SELECT * FROM users LIMIT 10 OFFSET 20

Pagination (skip 20, take 10)

SELECT * FROM users ORDER BY age DESC

Sort descending

Filtering & Logic 6

WHERE name LIKE 'A%'

Prefix match

WHERE name LIKE '%son'

Suffix match

WHERE age BETWEEN 18 AND 30

Range

WHERE id IN (1, 2, 3)

Set membership

WHERE a IS NULL

Null check

WHERE a AND b OR c

Logic (AND precedes OR)

Aggregation & Grouping 5

SELECT COUNT(*) FROM users

Count

SELECT AVG(age) FROM users

Average

SELECT city, COUNT(*) FROM users GROUP BY city

Group by city

HAVING COUNT(*) > 5

Filter after grouping (on aggregates)

SELECT MAX(age), MIN(age) FROM users

Max / min

JOIN 5

FROM a JOIN b ON a.id = b.a_id

Inner join

FROM a LEFT JOIN b ON a.id = b.a_id

Left join (keep all of a)

FROM a RIGHT JOIN b ON a.id = b.a_id

Right join

FROM a CROSS JOIN b

Cartesian product

SELECT * FROM a NATURAL JOIN b

Auto-join on same-named columns

Window Functions 4

ROW_NUMBER() OVER (ORDER BY age)

Row number

RANK() OVER (PARTITION BY city ORDER BY age)

Rank (gaps on ties)

SUM(amount) OVER (PARTITION BY user_id)

Partitioned running total

LAG(price) OVER (ORDER BY date)

Previous row value

DML & Transactions 5

INSERT INTO t (a, b) VALUES (1, 'x')

Insert

UPDATE t SET a = 2 WHERE id = 1

Update

DELETE FROM t WHERE id = 1

Delete

BEGIN; ... COMMIT;

Commit transaction

ROLLBACK;

Rollback transaction

DDL 4

CREATE TABLE t (id INT PRIMARY KEY, name TEXT)

Create table

ALTER TABLE t ADD COLUMN age INT

Add column

DROP TABLE t

Drop table

CREATE INDEX idx_name ON t(name)

Create index

Tips

AND has higher precedence than OR — use parentheses for complex conditions.
Columns in GROUP BY must appear in SELECT (except aggregated columns).
LIKE case-sensitivity depends on the database collation.
Wrap data changes in BEGIN; and COMMIT only after verifying.

Official References

Each command links to its official documentation below, so you can verify the latest usage and read deeper.

PostgreSQL SQL

Maintained by LaoHand

Publicly updated on Aug 2, 2026, continuously proofread against official docs.

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