Reference

SQL Query Formatting Guide

Readable SQL is easier to debug, review, and change. A few simple habits go a long way.

SQL ignores whitespace, so formatting is purely for humans. Consistent layout makes it obvious what a query does and where to make a change.

The habits that matter most

Put each major clause (SELECT, FROM, WHERE, GROUP BY, ORDER BY) on its own line.
One column per line in SELECT once you have more than two or three.
Indent JOIN and AND/OR conditions under their clause.
Use short, meaningful table aliases (c for customers, o for orders).
Pick one case convention. Lowercase keywords are common and easy to read.

Before

Hard to scan

select c.first_name,c.last_name,count(*) from customers c join orders o on o.customer_id=c.customer_id where c.is_active=true group by c.first_name,c.last_name having count(*)>2 order by count(*) desc

After

Same query, readable

select   c.first_name,
         c.last_name,
         count(*) as order_count
from     customers as c
join     orders    as o on o.customer_id = c.customer_id
where    c.is_active = true
group by c.first_name, c.last_name
having   count(*) > 2
order by order_count desc

Dialect note

The Playground has a Formatbutton that tidies your query automatically (powered bysql-formatter in DuckDB mode). Handy for cleaning up a query you pasted in.

Lesson

Reading SQL Error Messages

Use error messages as clues.

Lesson

Debugging SQL Queries Step by Step

Shrink a query and check one piece at a time.

Lesson

Wrong SQL Results Without Errors

Catch silent query logic bugs.

Lesson

Formatting SQL Queries for Readability

Make queries easier to scan and debug.